Black Forest Yule log

For the pastry cream, put the yolks, corn  our, cocoa powder and 45g light brown sugar in a large bowl with a pinch of salt and whisk with an electric hand mixer until smooth and creamy. Put the remaining 25g light brown sugar and the milk in a medium saucepan and whisk to combine. Set over a medium heat and bring to a simmer. Pour the warm milk over the yolk mixture, whisking as you pour, then scrape the combined mixture back into the pan and return to a medium heat. Whisking constantly, cook for 1-2 minutes, until it starts to bubble and has thickened. Once it bubbles, cook for another minute, then scrape back into the bowl. Add the butter and 65g chopped chocolate, then whisk until melted and a smooth cream forms. Cover with damp baking parchment and chill for at least 4 hours (up to 24 hours).

For the cake, preheat the oven to 180ºC/160ºC fan/gas 4. Lightly grease the base of a 34x23cm rimmed baking tray and line with baking parchment. Put the egg whites in a large bowl and the yolks in a separate large bowl. Add 40g sugar to the whites with the cream of tartar and a pinch of salt. Whisk with an electric hand mixer on high speed until it holds soft peaks; set aside. Use the electric hand mixer to whisk the yolks with the remaining 40g sugar until thick and pale. Mix in the   our, cocoa powder and corn  our to form a smooth paste. Add the oil and milk and mix until combined. Carefully fold in the whites, in three additions. Pour the batter into the prepared tray and gently level out. Bake for 16-18 minutes or until the cake feels firm and springy.

Transfer the cake (in its tray) to a cooling rack. Place a sheet of baking parchment on the work surface and dust with a ne layer of cocoa powder. Run a sharp knife around the edge of the cake and carefully invert onto the cocoa-dusted parchment. Peel away the top layer of baking parchment. While the cake is still warm, roll up with the parchment from the short end. Wrap in a clean tea towel and set aside until cooled.

To assemble, beat the pastry cream until smooth. Use a balloon whisk to whip the double cream to soft peaks. Unroll the cake and spread the cherry preserve evenly over the surface. Spread about ¾ of the pastry cream over the cake in a thin layer. Add ¾ of the whipped cream on top in a thin layer. Carefully roll up the cake and transfer to a serving plate. Spread the remaining pastry cream over the cake, then repeat with the cream. Grate the remaining chocolate over the cake and decorate with fresh cherries. Serve straight away or chill for up to 24 hours.