Four 4/4 Cake

Beat the butter, sugar and egg yolks till a homogeneous light mixture. Sift the flour and slowly add to the batter, stirring constantly. In a separate bowl, beat the egg-white until very stiff. Preheat the oven on 170 C. With a spatula, slowly and carefully add the egg-white to the batter. Grease a 21cm diameter round mould with butter and dust some flour over it. Fill the mould with the batter until 3/4th filled. Bake on 170 C for 45 minutes, or : stop baking when you put a knitting needle in the cake and nothing sticks on it. After baking, remove immediately out of the mould and cool the cake on a tray.