For the apple-nut foam slices, stir the margarine until fluffy, add the yolks. Then stir in the sugar, nuts and flour with baking powder. Pour into a greased, floured cake baking pan.
Peel and thinly slice the apples, mix with vanilla sugar and cinnamon. Spread on the dough and bake at 180°C for about 45 minutes. The apples should be very soft.
For the mousse, beat the egg whites to snow and let the sugar trickle in. Spread on the apple mixture and bake for another 10 minutes until the snow is browned.