Preheat the oven to 160C/gas 3/fan 140C.
Grease a 850ml/1½ pint baking dish with butter.
Cut the panettone into slices, leaving the crusts on.
Cut the slices in half and arrange them in the dish.
Whisk together the eggs, cream, milk, vanilla extract and sugar.
Pour over the panettone.
Put the dish in a roasting tin and pour hot water around it to a depth of about 2.5cm/1in. Bake for 35 minutes until the pudding is just set.
Dust with icing sugar.
Serve with ice cream or whipped cream.