How to make
Separate the egg whites from the egg yolks. Beat the whites with a pinch of salt to stiff snow.
Separately, beat the yolks with the softened butter and the sugar, add the flour that you've sifted with the baking powder. Mix with the whites. Pour the resulting mixture into a buttered and floured cake form.
Cover the layer with the topping. To make it, mix the cut plums with the sugar, breadcrumbs, biscuits, walnuts and cinnamon. Bake in a preheated 360°F (180 °C) oven for 40-45 min.