Black Forest trifle

Grate some chocolate off the bar and set aside for the decoration. Break up the rest of the chocolate into a small bowl and microwave, or put over a pan of hot water, until melted. Put the custard in a large jug and warm it in the microwave for 2 mins. Stir well, then stir in the melted chocolate. Cover and leave to cool. Cut the roulade or cake into 6 slices and then break these up into the trifle bowl. Pour the syrup from the can of cherries into a small pan and boil for 5 mins to reduce it by half — about 5tbsp. Put the cherries on the cake in the dish. Add the Marsala to the syrup and then spoon it over the cake. Spoon the cooled custard over. Chill. Whip the cream with the icing sugar to soft peaks (add a little more Marsala, if you like). Spoon it on top of the trifle. Top with fresh cherries, if using, and sprinkle with the chocolate.