Preheat the oven to 170?C, then start by making the custard. Warm the milk on a medium heat until it?s just starting to get frothy (but don?t let it boil). Meanwhile, mix together the egg yolks and caster sugar into a thick paste.
Slowly pour the warm milk into the bowl with the eggs and sugar, stirring all the while, until smoothly combined.
Roughly tear the croissants into pieces, and spread each piece with just a little marmalade ? don?t go too overboard. Fill each of your ramekins with croissant pieces and tuck the chocolate chips in between. Pour the custard over the top so that it nearly fills each ramekin, and then sprinkle with brown sugar.
Pop the ramekins in the oven and bake for 30 minutes. Sprinkle with icing sugar and serve hot or cold, with cream, ice cream or just by itself.