Melt the chocolate with the butter. Mix the egg yolks with the sugar and add to it. Beat the egg whites until stiff and fold in with the flour. Bake at 200 ° on a smaller, flat baking sheet for approx. 25 minutes and cut into squares when it has cooled down (brownies) or bake in a cake tin for approx. 55 minutes. The inside of the cake remains slightly liquid. (Double the amount is needed for a large baking sheet)