Frozen bûche de Noël

1.For sponge, preheat oven to 180C and line a 27cm x 37cm oven tray with baking paper. Whisk eggs in an electric mixer on medium-high speed until light and fluffy (6-8 minutes). Meanwhile, stir sugar and 1½ tbsp water in a small saucepan over high heat until sugar dissolves, then bring to the boil without stirring. With motor running, add hot syrup to eggs and whisk on medium speed until mixture cools and holds a thin ribbon (6 minutes). Sieve in flour and cocoa, fold to combine, then fold in butter. Spread batter evenly in prepared tray and bake until sponge springs back when gently pressed (8-10 minutes). Carefully turn out onto a clean tea towel lined with baking paper and dusted with cocoa and peel baking paper off base of sponge. Loosely roll sponge in tea towel, starting from a long edge, and leave to cool (30 minutes).

2.For hazelnut semifreddo, roast hazelnuts on an oven tray at 180C, shaking occasionally, until browned (8-10 minutes). Rub hazelnuts in a tea towel to remove skins, then chop. Melt chocolate in a bowl over a saucepan of simmering water, ensuring the bowl doesn’t touch the water and stirring occasionally until smooth (2-3 minutes). Whisk eggwhites in an electric mixer until soft peaks form (1-2 minutes), then add sugar a tablespoonful at a time, and whisk until mixture is thick and glossy (2-3 minutes). Whisk cream and crème fraîche in a separate bowl to soft peaks. Fold melted chocolate into eggwhite mixture, then fold in cream mixture, followed by 70gm chopped hazelnuts (reserve remainder for serving).

3.Unroll sponge, spread evenly with semifreddo, then reroll. Wrap in baking paper, then plastic wrap and freeze until firm (8-10 hours). Remove bûche de Noël from freezer 30 minutes before serving. Dust with cocoa or icing sugar, scatter with raspberries and remaining roasted hazelnuts, and serve with thickened cream.