Chocolate Peanut Butter Cake

Ingredients

• unsalted butter — plus extra for greasing200 g
• cocoa powder50 g
• dark brown soft sugar100 g
• caster sugar125 g
• vanilla extract — 2 tsp10 ml
• plain flour225 g
• baking powder — 1 tsp4.5 g
• bicarbonate of soda — ½ tsp2.3 g
• large eggs — at room temperature2 ea
• icing sugar — for the buttercream300 g
• unsalted butter — softened, for the buttercream150 g
• smooth peanut butter200 g
• vanilla extract — 1 tsp; for the buttercream5 ml
• fine sea salt — ¼ tsp1.5 g
• double cream60 ml
• dry roasted peanuts — chopped35 g

Method

1. Heat the oven to 180°C/160°C Fan. Butter two 20 cm sandwich tins (not loose-bottomed, as this is a runny batter) and line them with baking parchment.
2. Cut the 200 g butter lengthways into four pieces and put into a heavy-based, fairly wide saucepan over gentle heat. Add 250 ml just-boiled water and whisk in the cocoa and both sugars; keep on a low heat, whisking gently, until the butter has melted and the mixture is smooth. Remove from the heat, stir in the 2 tsp vanilla and let stand for 5 minutes.
3. Mix the flour, baking powder and bicarbonate of soda in a bowl. Whisk the eggs together in a small jug.
4. Pour the eggs gradually into the pan, whisking all the while, until completely absorbed. Then whisk in the flour slowly and gently until you have a smooth batter, and pour evenly into the tins.
5. Bake for 18–20 minutes, until the cakes are shrinking away at the edges and a cake tester comes out cleanish (it is a damp cake, so a few crumbs are fine). Cool on a rack for 10–15 minutes, then turn out, or leave in their tins until cold.
6. For the buttercream, sift the icing sugar. In a large bowl, beat the softened butter and peanut butter together for 3 minutes in a mixer (5 with a handheld whisk) until light and fluffy, then beat in the vanilla and salt.
7. At a slightly lower speed, add the icing sugar a spoonful at a time until half is in, then the rest in 3 batches. Turn the speed up and beat for 2 minutes (3 by hand-held whisk), scrape down the sides and beat again briefly.
8. Still beating, add the cream a tablespoon at a time, then keep beating for 4 minutes (6 with a handheld whisk) until soft, aerated and moussy.
9. Place one cake flat-side up on a plate and spread with about a third of the icing right to the edges. Top with the second cake, domed-side up, and spread another third over the top.
10. Spread the remaining buttercream around the sides to cover and smooth, then decorate with the chopped peanuts.