Add the custard to a pan with the chopped chocolate, and heat on a low heat together until smooth.
Leave to cool fully.
Cream
Add the double cream to a bowl, add the icing sugar and whisk to soft peaks.
Swiss roll/Sponge
Slice the chocolate swiss roll into 1-2cm size slices, or chop up pieces of chocolate cake.
Sprinkle over 4-5 tablespoon of kirsch if using.
Assembly
You can build the trifle, however you want.
Layer the slices of the swiss roll around the edge of the trifle bowl at the bottom, and a few on the bottom as well.
Pour over half of the chocolate custard and spread.
Add on half of the kirsch soaked cherries, and half of the brownie bites.
Spread on half of the whipped cream, and pour on the one layer of cherry jam.
Repeat this again, finishing with the rest of the whipped cream on top.
Decorate the top with the fresh cherries and some grated chocolate!
Leave it to set for an hour in the fridge. Serve!
Notes
This sort of dessert is best served on the day of making, or the day after. Once made, it can last a few days in the fridge, I wouldn't recommend freezing, however.