Whip cream with sugar until it forms stiff peaks. Gently fold in custard. Stir in 1 tbsp. rum to flavour and refrigerate for 1 hour.
Slice each cake in half to make equal layers.
Place one layer on a large, deep platter and sprinkle with a little rum. Cover with some of the cream mixture. Sprinkle with candied peel and grated chocolate.
Repeat with remaining layers, cream, peel and chocolate.
Refrigerate cake at least 8 hours before serving.
*Prepared custard cream can be found in the dairy section of the supermarket. Use remaining custard as an accompaniment for cakes, pies, ice cream or any other dessert.