Melt the chocolate in a bain marie over a medium heat. Take off the heat and pour in the custard, mixing to combine. Cover with cling film and cool.
Arrange the brownies in the base of a trifle bowl. Drain the jars of cherries and scatter over the brownies. Drizzle over 100ml cherry brandy. Lightly whip the cream with the crème fraîche and icing sugar until soft peaks form. Spoon the cooled chocolate custard over the brownies, followed by the cream.
Decorate with grated chocolate and fresh cherries, if you like.