Cut the hot cross buns in half across the middle. Spread each slice with the marmalade.
Arrange the halves of hot cross buns in the dish, stack them up against each other, until you have used them all up, sprinkle in chunks of chocolate, then set aside.
Crack the eggs into a bowl and add the milk, cream and sugar. Use a balloon whisk or a fork to whisk until combined.
Pour the custard over the prepared hot cross buns and butter and leave to stand for 30 minutes. Preheat the oven to 180C/160C fan/gas mark 4.
Break the butter into small pieces and scatter over the top of the pudding.
Place the dish into the oven and bake for 30-40 minutes, or until the custard has set and the top is golden-brown.