Splice the vanilla and let it boil with the milk and sugar; smooth the cornflour with a spoonful of water, thicken the milk with it, and let it cook gently for 2 or 3 minutes; remove the vanilla. Have ready the whites of eggs whipped to a stiff froth, drop it in spoonfuls in the boiling milk; let it simmer for a few minutes until the egg snow has got set, remove the snowballs with a slice, and place them in a glass dish. Let the milk cool a little; beat up the yolks of the eggs, mix them carefully with the milk, taking care not to curdle them; stir the whole over the fire to let the eggs thicken, but do not allow it to boil. Let the mixture cool, pour the custard into the glass dish, but not pouring it over the snow; serve when quite cold. Half the quantity will make a fair dishful.