Step 2

Beat the 8 egg whites to stiff peaks, then add the 7oz sugar in small batches, whisking constantly. Add the egg yolks one by one, whisking. Gently fold in the flour-cocoa mixture.

Step 3

Pour into the lined pan and bake for 35 minutes. Cool for 5 minutes, remove from pan and re-line the pan with fresh parchment.

Step 4

Make the walnut meringue: whisk the 5 egg whites to stiff peaks, then gradually whisk in the second 7oz sugar, 1 tbsp at a time. Fold in the chopped walnuts (reserving some for decoration), the 1 tbsp flour and potato starch. Spread into the re-lined pan and bake for 40 minutes at the same temperature. Cool completely, about 30 minutes.

Step 5

Make the chocolate ganache: heat the cream over low heat, then remove from heat. Pour in the chocolate chips and stir until melted and shiny.

Step 6

Cut both the sponge and meringue into two layers each. Assemble: bottom sponge layer, then a meringue layer with walnuts sprinkled on, then another meringue layer, then the top sponge layer. Cover the top with chocolate ganache. Decorate with reserved walnuts.

Step 7

Refrigerate for 1–2 hours before serving.