Chocolate Peanut Butter Birthday Cake

40 Comments on Chocolate Peanut Butter Birthday Cake
chocolate peanut butter cake

Squidgy chocolate cake with creamy peanut butter frosting

David Lebovitz once said that the best thing about being a pastry chef is that your kitchen colleagues have to be nice to you 364 days a year. Why? Because on the 365th they want you to bake them a birthday cake. While I’m no pastry chef and have never worked in a commercial kitchen, when it comes to baking cakes for friends, I know exactly where he’s coming from.

One of the things I love most about baking is being able to share what I make with those around me. A cake can be a talking point, a celebration in itself and (for me anyway) often a better way of expressing love for the person in question than any other present might be. Birthday cakes are particularly personal, the one opportunity each year to take centre stage, to call the shots, to cut yourself the biggest slice, eat seconds and thirds and lick off extra icing if you should so choose (not, of course, that I’d ever do something like that . . .)

chocolate peanut butter cake

A thick layer of slightly salty sweet peanut butter frosting

Almost exactly a year ago, I drove this toffee popcorn cake over to Tooting to give to one of my oldest friends (in terms of how far we go back, rather than ‘oldest’ implying anything to do with her age). In the unseasonally warm sunshine we sat out in the garden and ate thick slices from pale blue crockery with silver teaspoons, enjoying the crunchy popcorn, the toffee sweetness, the surprising hidden pop.

Twelve months have passed and the girl in question is now not only an even older friend, but also one of my bridesmaids to be. As her birthday drew closer, the question of a cake came around and I asked if she had any particular flavour or inspiration which I could work with. The answer? Reese’s peanut butter cups, an absolute favourite of the birthday girl’s (and half of the rest of the world it would seem if you have a look online).

chocolate peanut butter cake

‘That’ chocolate cake makes the base of this delicious dessert

When it comes to peanut butter-based recipes, America reigns supreme. Stateside blogs are filled with amazing peanut butter creations, from the sublime to the ridiculous (think double Reese’s Peanut Butter Cup stuffed chocolate chip cookies), but after a lot of Googling (and a little drooling) I decided to stick with something that was classic, simple and delicious.

The chocolate cake I’ve used for the base is that chocolate cake. The first time I made this cake, I tarted it up with a whiskey syrup, wondering whether the extra soaking is what made it so wonderfully moist. It certainly adds a little something, but the unadorned batter is every bit as deliciously damp and darkly chocolaty, the perfect foil for a thick, creamy, slightly salty, whipped peanut butter frosting.

The frosting recipe comes from Annie’s Eats. If you’ve not yet discovered her blog, you’re in for a treat. Annie’s baking and cakes are second to none and her various buttercream recipes (chocolate chip cookie dough buttercream anyone?) are out of this world. This frosting is no exception: sweet and salty, light and fluffy, rich and nutty and utterly delicious.

chocolate peanut butter cake

Creamy, rich & delicious

After a couple of friends cancelled at the last minute, we were left with a whole cake to consume between just five people on the actual day. We made valiant inroads and the rest was wrapped up by the restaurant in giant parcels to take away. I can confirm that the (slightly squashed) cake was as deliciously decadent the next day. If not more so (though this may be something to do with the fact that it was eaten for breakfast).

Apologies for the slightly boring snaps of a single slice of cake and lack of a full photo showing it in all its peanut butter cup studded glory. I hadn’t actually planned to blog this recipe, but embarking on the final slice I realised it was too delicious not to share and quickly took a couple of photos before forking the remains into my mouth.

Chocolate Peanut Butter Birthday Cake

(makes one two tier 20cm round cake)


For the cakes
225g plain flour
350g caster sugar
85g cocoa powder
1½ tsp baking powder
1 tsp bicarbonate of soda
2 large free range eggs
250ml full fat milk milk
125ml vegetable oil
2 tsp vanilla extract
250ml boiling water

For the frosting (from Annie’s Eats)
175ml double cream, chilled
390g icing sugar, sifted
335g unsalted butter, at room temperature
255g creamy peanut butter
1 heaped tsp vanilla extract
Pinch of coarse sea salt

To assemble
Peanut butter cups, quartered (or mini peanut butter cups, halved)


For the cakes
Preheat the oven to 180C. Grease and line two 20cm round cake tins.

Place all of the ingredients, except the boiling water, into the bowl of a free standing mixer. Beat until well combined. You could also do this in a large mixing bowl with an electric whisk or wooden spoon.

Add the boiling water to the mixture, a little at a time, until smooth. Don’t worry if the cake batter looks very liquid, this is how it should be.

Divide the cake batter between the tins and bake in the oven for 25-35 minutes, or until the top is firm to the touch and a skewer inserted into the centre of the cake comes out clean.

Remove the cakes from the oven and allow to cool completely in their tins before icing.

For the frosting
Combine the double cream and 30g icing sugar in a large clean bowl and whisk until light, fluffy, stiff peaks form. Be careful not to overmix.

In an electric stand mixer fitted with the paddle attachment, combine the butter and peanut butter.  (You could also do this with a wooden spoon and a bit of elbow grease.) Beat on medium-high speed until smooth, about 45 seconds.

Add the remaining icing sugar to the bowl a little at a time, mixing slowly so it doesn’t all billow up in the air. Once loosely combined, turn the speed to full and beat for 2 minutes.

Add the vanilla extract and salt, and continue to whip on high speed until very fluffy, about 4-5 minutes, scraping down the sides of the bowl as needed.

Using a large spatula or metal spoon, gently fold one third of the whipped cream into the peanut butter mixture before adding the rest and folding carefully to combine.

To assemble
Place one cake on a serving plate or cake board, securing with a small amount of frosting. Spoon approximately one third of the frosting onto the cake and smooth over the whole surface, allowing some to spill over the edges.

Top with the second cake and spoon over another third of frosting, smoothing it flat to form the ‘crumb coat’. Pop in the fridge to firm up for 30 minutes or so, then apply practically all of the final third of the frosting to create a smooth layer. Reserve a little frosting to pipe round the top edges if you like then stud with pieces of peanut butter cup.

The frosting starts to soften if left out of the fridge for too long so serve immediately or keep somewhere cool, a larder would be ideal.

40 RESPONSES TO Chocolate Peanut Butter Birthday Cake

  1. Amy -

    Oh you’re right about that chocolate cake being squidgy– it looks like some of the best chocolate cake I’ve seen on the web. It is wonderful to bake these treats for friends, isn’t it? Best present to give, in my opinion.

  2. This looks wonderful! You mentioned this cake to me earlier and I’m so glad you posted it. Anything with peanut butter and chocolate always tempts me, especially this cake since I know how delicious THAT chocolate cake is. I’m sure the peanut butter buttercream is heavenly with it!

  3. I couldn’t agree more about sharing cakes and bakes- at least half of the enjoyment in baking for me is surprising friends or work colleagues with a little something! And I’ve no doubt your friend was absolutely delighted with this lovely cake.

  4. The pic show the exact type of chocolate cake I love, dense and fudgy but still undeniably cakey. It sounds like a dream with the peanut butter filling! But I must admit I´m still a fan of the whiskey one with choco frosting…!

    • Amy – what a lovely comment, thank you so much! And yes, baking for friends is the best 🙂

      Connie – it’s such a good combo – the salty sweetness of the peanut butter really offsets the chocolatiness of the cake. Wish I still had some left!

      Kate – it’s so true, I love the reactions on peoples’ faces 🙂

      Paula – the whiskey one is pretty hard to beat . . .

      Lauren – haha thank you!

  5. That. Looks. Amazing.

    You’ve made my mouth water!

  6. another reminder that i have to try making “that chocolate cake”! looks so delicious.

  7. Hehe I never looked at the life of a pastry chef like that! 😛 And that cake looks so, so moist, I love it! 😀

  8. This is pretty much my favourite every flavour combination – I may even make it for my own birthday next month!

  9. jamielifesafeast -

    I have a similar chocolate cake recipe to this and love it. It is almost the only cake I bake on my own birthday! Love the whiskey in it – must taste incredible! And mmmmm peanut butter frosting. I love peanut butter but sadly my French men would never eat peanut butter frosting (I’ve been dying to make it). I’d be forced to consume the entire cake myself.

    • Peonut – just wait til you try a slice!

      Lucky Bakes – you really do, it’s so good.

      Lorraine – it’s divine – fudgy without being heavy or overly dense.

      Kathryn – you should, it’s such a crowd pleaser 🙂

      Jamie – could you not convince them to try some? What’s the worst that could happen? (you end up eating it all to yourself, not necessarily a bad thing . . .)

  10. laythetable -

    I bet all your friend’s friends were green with envy – looks incredible and no doubt tastes amazing. The only thing is that when you make such great birthday cakes, I bet no-one would dare make you one on your own birthday for fear of your high baking standards!

  11. This looks utterly divine! I bet your friends loved it! Peanut butter seems to be having a moment as there are quite a few PB bakes about…but I have to say this one looks particularly fab! I’ve never made anything with PB but I’m thinking I ought to! 🙂

  12. I’m glad you decided to share this recipe because the cake looks divine!!! The cake looks so deliciously moist and fudgey.

  13. So fudgey and awesome! Anything with peanut butter is a winner with me 😀

  14. So glad you decided to post this recipe just before the last slice was finished, I am one of those choc/PB combo lovers.

    • Becs – I don’t know that they get a chance to offer, I love baking my own birthday cake! 🙂

      Laura – oh, peanut butter and chocolate is the most heavenly baking combination, you have to give it a go.

      Jennifer – thank you and yep, that pretty much sums it up. So good.

      Nic – me too!

      Nuts About Food – I wish I could have snapped the whole cake, the frosting swirls and peanut butter cups just made you want to dive in!

  15. This looks absolutely amazing! What a great way to celebrate a birthday 🙂 I’m not even a huge peanut butter fan, but this looks so perfect I wish I could reach through the screen and grab myself a slice! 😀

    • Amanda – consider yourself signed up 🙂

      Dana – thank you and glad I’ve gone some way to converting you into a peanut butter fan 😉

  16. ‘That’ chocolate cake with a salted peanut butter frosting looks incredible. I think you’ve somehow managed to surpass your chocolate whiskey cake and make something which looks even more decadent and delicious.

  17. How could you not have planned to blog such a glorious cake. Apart from the squidgyness of the cake and the salty creaminess of the icing, I really like the colour contrasts – such a dark cake is beautifully offset by the light icing. What a lovely present.

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  20. Fiona -

    Thanks for blogging about this cake. I’ve been looking for chocolate/peanut butter cake recipe for a little while to make for a birthday.

    It looks absolutely delicious.

    • Ah, my pleasure – would love to see a pic if you make it!

  21. Steph -

    This looks divine!

    How many do you think this would feed? Been looking at triple layer cakes, but this sponge looks so tasty, I want it make this one for my fella’s 30th 🙂

    • thelittleloaf -

      It is! Hmmm, quite a lot of people, maybe 16?

      • Steph -

        Ah, thank you. That’s perfect! Thanks for posting the recipe

  22. Laura -

    I just made this for hubby’s birthday….wow wow wow! I have never baked a cake from scratch in my life and I was a little worried when I saw how liquidy the mix was, I thought I’d really messed up! After 35 minutes in the oven it was perfect and they frosting is incredible. Thanks so much for posting this 🙂

    • admin -

      I’m so pleased! I’d love to see a photo 🙂 xxx

  23. Jessika -

    Could you please convert the recipe into cup measurements for me? I would love to make it for my birthday.. but I don’t know how to convert grams into cups.
    Thanks! It looks delicious!

    • Hi, I’m afraid I don’t give cup measurements as I think scales give a much more accurate bake! They’re well worth the investment if you’re a keen baker 🙂 Kate x

  24. Elspeth -

    Thank you for the recipe! This might be the tastiest, most decadent cake I’ve ever eaten. My 2 year old helped decorate it so it’s not the most polished finish though. I can’t work out how to upload a photo I’m afraid!

  25. Inga -


    Love the look of this cake and would like to make it for my husbands birthday! Can I substitute oil for butter? And if yes, how much butter would I need? And would I need to melt butter first?

    Thank you for your answer in advance!

    Inga x

    • admin -

      Hi ingrid, I’m afraid I’ve not tested the recipe with butter. It should work with an equal substitute but will affect the texture. If you do try it, let me know how you get on! Xxx

  26. Fiona Grieveson -


    I just test-made this cake for my son’s birthday on Thursday, but although it is tasty it came out very dense and wet, without the hint of crumb your photo shows.
    I stuck to the recipe so trying to figure out why….maybe I over-whipped the batter? Or should I try reducing the water a little?
    Any feedback greatly appreciated thanks!!


  27. Hannah -

    I’ve just made the cake, is it right that it has shrunk/shrivelled slightly when brought out of the oven?

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