Softened butter mix with powdered sugar to graying. Put out one by one the yolks, then the yogurt and flour mingled well with baking powder, vanilla and starch. Finally added egg whites broken down into a thick foam. 2/3 of the mixture is poured into the form. The rest was put 1 tbsp yogurt, powdered sugar and cocoa. This mixture was poured onto the other. Bake in a moderate oven. All products of the glaze is mixed and boiled until thickened. Once baked the cake is removed and turned into a dish. Pour with glaze and sprinkle with plenty of walnuts.