Chop the chocolate small, or grate it. Put it in a pan with a quarter of a pint of the milk and boil it until smooth. Watch it carefully, as it easily burns.
Mix the cornflour smoothly and thinly with two tablespoonfuls of the milk; add it and the rest of the milk to the chocolate, and stir until it boils. Then draw the pan to the side of the fire and let it cool. Separate the yolks and whites of the eggs. Beat up the yolks, and when the milk and chocolate are a little cool add them, stirring them in well. Flavour with vanilla. Pour the mixture into a buttered pie-dish, and bake half an hour. Beat the whites to a stiff froth, add the sugar lightly, and heap this over the top of the pudding; sprinkle a table-spoonful of sugar over the top and bake very slowly until the meringue is a pale biscuit colour. It will take about fifteen minutes. Serve at once.