Oreo cookie chocolate trifle

Method

1. First make the custard: heat the milk in a saucepan over a medium heat until steaming hot but not boiling. Take off the heat and add the grated chocolate, stirring to help it dissolve.
2. In a medium mixing bowl, whisk together the egg yolks and sugar, then sprinkle over the cornflour and mix it in until smooth. Slowly pour over the chocolate milk, whisking to incorporate it, then transfer the mixture back to the saucepan. Cook over a medium heat, stirring all the time, until the custard thickens. Take off the heat and set aside to cool a little, then stir in the mascarpone. Lay a piece of damp compostable baking paper on the surface to stop a skin forming and chill for 30 minutes (see Make Ahead).
3. Arrange the trifle sponges and full-size Oreos in the base of your trifle dish, then spoon over the chocolate custard and smooth the surface. Cover and chill for 2 hours to allow the custard to set fully.
4. Just before serving, whip the double cream with a balloon whisk to reach soft peaks (a peak will form when you lift the whisk out of it, but will fall back into the mixture within a few seconds). Spoon the cream over the trifle. Dust the trifle with cocoa powder, then arrange the mini Oreos on top, roughly chopping some of them for extra texture. Dive in!