Flourless chocolate, hazelnut and buttermilk cake

1.Preheat oven to 190C, and butter a 22cm diameter cake tin and line with baking paper.

2.Roast hazelnuts on an oven tray until golden (5-8 minutes). While warm, tip into a tea towel and rub to remove skins, then finely chop.

3.Melt chocolate and butter in a heatproof bowl over a saucepan of simmering water, stirring occasionally until smooth. Remove from heat, and stir in buttermilk, cocoa and egg yolks.

4.Meanwhile, whisk eggwhites until frothy in an electric mixer, then, while whisking, gradually add the sugar and whisk until glossy soft peaks form. Fold in chocolate mixture in batches along with hazelnuts, pour into prepared tin and bake until cake rises and cracks at the top (25-30 minutes). Cool in tin, gently pressing on top as it cools so it falls back evenly, then remove from tin, dust with cocoa and serve. Cake will keep for 2-3 days stored at room temperature in an airtight container.