Chocolate and peanut butter snack cakes

Heat the oven to 180C/fan 160C/gas 4 and lightly butter a 23cm square cake tin, lining the base with a piece of baking paper.

To make the cake, put the butter and sugars into a large bowl and beat with electric beaters for about 5 minutes until light and fluffy. Add the eggs a little at a time, beating until fully combined before adding more. Mix the flour, baking powder and cocoa powder. Fold the flour mixture into the butter and sugar, until fully combined. Pour in the milk and mix briefly until fully combined. Scrape the batter into the prepared tin and smooth the top. Bake for 25-30 minutes or until the cake springs back to the touch. Allow the cake to cool in the tin for 15 minutes before carefully turning out onto a wire rack to cool completely.

To make the buttercream, put the egg whites and sugars into a large, heatproof bowl and sit over a pan of simmering water stirring regularly until the sugar has dissolved and the mixture is warm. Remove from the heat and whisk with electric beaters on high speed until the mixture forms stiff peaks and comes to room temperature. Add the butter a little at a time, beating until fully combined and a smooth buttercream has formed. Mix in the peanut butter and a pinch of salt.

To assemble the cakes, use a long serrated knife to trim the top of the cake flat and then cut in half horizontally to get two even layers. Line the cake tin you used for the sponge with clingfilm and put the first layer of the sponge into the tin. Spread over the buttercream in an even layer. Top with the second cake layer and gently press together. Fold the excess clingfilm over the top of the cake and chill for 3 hours until firm.

When ready to assemble, use a serrated knife to gently saw the cake vertically into 9 equal-sized pieces. Put the cakes into the freezer while you melt the chocolate. Once ready, take the cakes one at a time from the freezer and dunk into the melted chocolate, coating completely. Use a large knife or spatula to lift the cake from the bowl and tap against the side to allow the excess chocolate to drip back into the bowl. Put the cakes onto a piece of baking paper, sprinkle with a few rainbow sprinkles and put the cakes into the fridge to set. Chilled, and kept in an airtight box, they will keep for 2-3 days.