Beat the yolks very well with the sugar. Add the other products without the egg, mix well and pour into a narrow tray covered with paper that you've coated with butter. Smear the bread on top with beaten egg and bake.
Remove the cooked bread from the tray, get rid of the paper and cut it into slices. Arrange them in the tray and lightly toast them.
Sprinkle with sugar and serve.