Peanut butter and jam brown butter sponge cake

Method

1. First make the brown butter. Cut the butter into small cubes and put in a small saucepan over a medium heat, keeping a close eye on it and swirling the pan every now and then. It will melt, then start to foam. Slowly you’ll see dark residue settling in the base and clear golden liquid on top. You’ll know when the brown butter is ready because it will darken and the sound as it bubbles will get quieter and almost stop (once the water content has evaporated there’s nothing to make that noise). Remove from the heat as soon as it’s ready, then strain through a fine sieve lined with a piece of muslin or kitchen paper into a suitable container. Transfer half to a bowl to use for the cake – you need it to be melted still but cooled a little. The half left in the container should go in the fridge once cooled – you’ll need to chill it for 2-3 hours until completely cold and solid before using it for the buttercream.
2. For the cakes, heat the oven to 170°C fan/gas 5. Line the bases of the sandwich tins with circles of baking paper but do not grease the tins. Sift the flour, cornflour and salt into a bowl, repeat a couple of times, then set aside.
3. In the bowl of a stand mixer with a whisk attachment or using an electric whisk, whisk the eggs, vanilla and sugar together for 2-3 minutes at a medium speed. Increase to high speed and whisk for 6-8 minutes, until light, pale and tripled in volume. Gently fold in the flour mixture in 3 or 4 additions, trying not to deflate the batter (use a large metal spoon and a figure-of-eight motion).
4. Stir 3 tbsp of the cake batter into the cooled but still melted brown butter. This step is called the tempering of the batter and it makes it easier to fold the butter into the airy batter. Gently pour the butter mixture down the edge of the bowl of cake batter, then fold it through (as above), making sure the batter in the bottom of the bowl is also fully incorporated.
5. Pour the batter in the prepared cake tins. Bake for 22-24 minutes or until the skewer comes out clean and it is springy to the touch. Cool the cake in the tin for 10 minutes, then gently run a palette knife around the edges of the tin and turn the cakes out on a wire rack. Peel off the paper and leave to cool completely.
6. For the jam, heat the oven to 160°C fan/gas 4. Double line a large shallow rectangular baking dish or tray 2 two sheets of baking paper, with the paper coming up the sides to contain the juices while baking. Add the sliced strawberries, lemon juice, salt and sugar and bake for 15 minutes. Add the raspberries and give it a stir. Bake for a further 10-12 minutes. Remove from the heat and mash the fruits slightly with the back of a spoon then leave to cool completely. You may find it to be very syrupy but as it cools it will thicken.
7. For the peanut crumb, line a baking tray with a sheet of baking paper. Spread the peanuts out in a single layer on it and set aside. Put the sugar in a medium saucepan and put over a medium heat. It will melt and slowly turn a golden amber colour – do not stir the sugar, just swirl the pan to help it cook evenly. Once the sugar is melted and golden, carefully pour it all over the peanuts. Leave to cool completely. Once cold, break into shards, then crush to make peanut crumbs, as chunky or as fine you like.
8. Once the remaining brown butter has completely chilled, make the buttercream. In the bowl of a stand mixer or with an electric whisk, beat the butter at a medium speed until light and fluffy (around 2-3 minutes). Add the icing sugar in 2-3 additions, beating for 2-3 minutes after each addition. Once all incorporated, beat on a high speed for a further 5-7 minutes. The buttercream will be light and fluffy. Add the peanut butter and beat for 1
   minute. Pour in the cold double cream, salt and vanilla paste and beat for 2-3 minutes until all combined and whipped.
9. To assemble the cake, put one of the sponges on serving plate or cake stand. Add half the peanut buttercream and spread it evenly. Use the back of a spoon to raise a sort of dam or low wall just inside the edge of the cake so it will hold the jam. Spoon the cooled jam into the centre of the cake – less is more here, you only need 4-5 tbsp. (You can always serve the extra jam on the side.) Sprinkle over a little of the peanut brittle. Sit the other sponge on top, gently pressing it down to secure. Spoon more of the buttercream on top of the cake, giving it a swirl pattern with the back of a spoon or a palette knife. Drizzle over some more of the jam. Finish with a generous sprinkle of the peanut brittle crumbs.