Preheat the oven to 180C. Lightly butter a square or oval ovenproof dish.
Cut the panettone slices in half and arrange the bread in the dish.
Scatter over the chocolate chips and orange zest.
Whisk together the eggs, sugar cream and milk. Pour this over the bread. Leave to soak for around 20 minutes, then sprinkle over the demerara sugar. Bake for 45-50 minutes or until the custard has set and has a slight wobble. If the top of the pudding looks like it is beginning to burn, cover the top with foil.