Make a light roux of 50 g butter and flour, dilute gradually with milk and boil until a thick sauce. As cool a sauce, add the egg yolks, salt and beaten hard whites. Spread the mixture into two greased pans with butter and bake in a hot oven. Brain is flooded with water and allowed to stand after a little skin is removed. Cut into small pieces. Stews in the remaining butter and add salt. Omelets filled with this stuffing, wrapping, cut into halves, sprinkle with chopped parsley and serve immediately.