Mix 4 egg yolks with 250 g sugar, water and oil until frothy. Mix flour and baking powder, carefully stir in alternately with egg whites made from 4 egg whites and poppy seeds. Spread the dough on a greased baking sheet.
Mix the butter, 150 g sugar, vanilla sugar and 4 egg yolks until frothy. Add the quark, custard powder and rum. Carefully fold in the 4 egg whites. Pour the mixture into a piping bag and spray onto the dough in a grid shape. Bake at 200 ° C for 50 minutes.