Make the caramel by heating the sugar in a casserole and leaving it to melt, without stirring. Once it turns a golden color, it's ready - be careful not to burn it.
Make the mixture for the cream by beating the eggs with the sugar in a bowl and adding the heated milk with vanilla.
Pour the warm caramel in a tray, cut the croissants into round slices and while still warm, arrange them next to each other on top of the caramel.
That way, the croissant slices will stick to the tray and not rise up to the surface.
Pour the cream mixture over them and put them in a preheated 356°F (180 °C) oven until the cream turns golden.
Leave them to cool for at least 4 hours.