Today is not for the faint of heart… Sure, this cake is not the healthiest option, but it is a sweet treat, not an everyday meal component. Make it. Eat it. Enjoy it. Share it.

Chocolate and Peanut Butter — a combination after my own heart. If you are craving an extra-rich chocolate cake with a thick peanut butter frosting and bites of crunchy salted peanuts, this cake is for you. This is one of the moistest cakes I have ever made. Every bite is sheer perfection.

This moist chocolate sponge with fluffy peanut-flavoured buttercream is inspired by Nigella Lawson's new book Cook, Eat, Repeat, and it is a truly decadent celebration bake. If you have a free-standing food mixer and a food processor, this cake will be a doddle to make — not that you cannot make it by hand, but it will count as a daily workout for all the effort involved.

The sponge cake is more like a deep, dense, fudgy chocolate brownie, likely from the batter being so liquid. Fabulous as this is, the super smooth and fluffy frosting makes this cake truly exceptional. The frosting is like a Snickers bar in mousse form. Surprisingly, the cake and frosting are not overly sweet, making peanut butter the star of the show. If you have a peanut butter lover in your life, this Chocolate Peanut Butter Cake will be their favourite forever.

Nigella recommends making a four-tier cake, but I used standard 20cm cake tins due to missing the ultra-shallow tins, and the cake turned out perfectly.

Do I Need Any Special Ingredients?

No, you don’t need fancy ingredients, but use the best quality you can afford for the ultimate flavour.

🔗 For help with conversions, see my Kitchen Conversions Guide.

Butter, salted: softened to room temperature for an ultra-moist crumb and fluffy frosting. Unsalted works too — just add a pinch more salt.

Soft light brown sugar: adds moisture and a slight toffee note to the sponge.

Golden caster sugar (superfine sugar): for sweetness and a fine, even crumb.

Cocoa powder (unsweetened cocoa powder): sift for a lump-free, intensely chocolatey batter.

Self-raising flour: gives lift without extra leavening faff.

Eggs: large, at room temperature so the batter emulsifies smoothly.

Vanilla paste/extract: rounds off both sponge and frosting.

Dark chocolate chips (semi-sweet chocolate chips): folded through for melty pockets.

Crunchy peanut butter: fabulous for texture; smooth works if you prefer a silkier finish.

Marshmallow fluff: the secret to a whipped, mousse-like peanut butter frosting.

Sea salt flakes (kosher salt): tiny pinch to sharpen flavours.

Salted peanuts (roasted peanuts): crushed for a savoury-sweet crunch on top.

Tips for Making the Best Chocolate Peanut Butter Cake

Use high-quality dark chocolate and cocoa powder for a deep, rich flavour.

Spread the batter evenly between tins to ensure uniform baking.

Allow cakes to cool completely before frosting to prevent melting.

Do not overbake — test with a skewer 5 minutes before the recommended time.

Storage and Make-Ahead Tips

Best enjoyed within a couple of days — it disappears quickly!

Store in the fridge if not serving immediately; bring to room temperature before serving for optimal taste.

Prepare frosting up to 1 day ahead and whisk briefly before using.

Freeze cakes (individually wrapped) for up to five months; fully defrost before assembling.

Chocolate Peanut Butter Cake

Prep: 30 mins | Cook: 18 mins | Servings: 16 slices

Ingredients

• Chocolate Sponge: 200g salted butter, 250ml hot water, 50g cocoa powder, 100g soft light brown sugar, 125g golden caster sugar, 1 tsp vanilla paste, 2 large eggs, 225g self-raising flour, 100g dark chocolate chips
• Peanut Butter Frosting: 300g icing sugar, 150g soft unsalted butter, 200g crunchy peanut butter, 100g marshmallow fluff, 2 tsp vanilla extract, pinch sea salt

Instructions

1. Heat oven to 180°C (fan 160°C / gas 4). Butter two 20cm sandwich tins and line with baking parchment.
2. Melt the butter gently and mix with hot water.
3. Combine dry ingredients in a bowl or a processor. Gradually add butter-water mixture, then eggs and vanilla. Mix until smooth, and fold in the chocolate chips.
4. Divide batter between tins and bake 16–18 minutes (check with skewer).
5. Cool cakes completely in tins before frosting.
6. For frosting: Beat butter, peanut butter, and marshmallow fluff until smooth. Add vanilla and salt, then gradually beat in icing sugar until fluffy.
7. Assemble: Place one cake layer on a plate, spread a third of the frosting. Top with a second layer, repeat. Frost sides, smooth top, and decorate with crushed peanuts if desired.

💡 Tip: Prepare frosting 1 day ahead and store in fridge; whisk briefly before using for extra fluffiness. Cakes can also be frozen individually for up to 3 months.

🌟 Recipe Variations

Nut swap: Try almond or cashew butter instead of peanut butter for a different flavour profile.

Chocolate twist: Add white chocolate chips or a drizzle of melted chocolate over the frosting for extra indulgence.

Mini cupcakes: Divide the batter into a muffin tin for smaller, single-serve versions — reduce baking time to 12–14 minutes.

Vegan option: Use a vegan butter substitute, flax eggs (1 tbsp flaxseed + 3 tbsp water per egg), and a dairy-free marshmallow alternative.

💡 Handy Hints / FAQs

Can I freeze this cake? Yes — bake the layers, wrap individually, and freeze for up to 3 months. Defrost completely before frosting.

Can I make the frosting ahead? Absolutely — store in the fridge for up to 1 day and whisk briefly before using.

Can I use smooth peanut butter? Yes, though crunchy adds texture and crunch to the frosting.

Do I need special cake tins? No, standard 20cm sandwich tins work perfectly; just line them well with baking parchment.

How do I get a really fluffy frosting? Make sure your butter is at room temperature and beat the frosting for 3–5 minutes until light and airy.

Would I Bake This Cake Again?

Absolutely! Next time, I might add chopped Reese’s peanut butter cups between layers to elevate the peanut butter flavour even more. What would you add?

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