unsalted butter for the tin
250g shelled hazelnuts
225g unsalted butter, softened
250g caster sugar
8 eggs, separated
finely grated zest of 5 lemons
65g plain flour
150g best-quality dark chocolate (70 per cent cocoa solids), grated
● Preheat the oven to 180C/gas 4. Butter a 30cm round cake tin that is 5cm deep, and line the base with greaseproof paper.
● Spread the hazelnuts in a small baking tin and toast in the oven for about 10 minutes or until their skins are loosened. Tip the hot nuts into a tea towel and rub to remove the skins. Coarsely chop the nuts in a food processor.
● Beat the butter and sugar together in an electric mixer until pale and light. Add the egg yolks, one by one, beating well.
● In a separate large bowl, beat the ricotta lightly with a fork. Add the lemon zest and chopped nuts.
● In a third large bowl, whisk the egg whites until they form soft peaks.
● Fold the egg yolk and butter mixture into the ricotta. Sift in the flour and fold it in.
● Finally, fold in the whisked egg whites. Spoon into the prepared cake tin and bake for 35 minutes or until set.
● Remove the cake from the tin to a plate and leave for 5 minutes then, while it is still warm, cover with the grated chocolate, which will immediately melt.