Beat the eggs, sugar and vanilla sugar in a hot water bath until creamy, then continue to beat without a water bath until the mixture has cooled. Stir in flour and butter.
Spread batter on a baking sheet lined with parchment paper and bake at 200 degrees e until golden brown. Turn out onto a sugar sprinkled tea towel, remove parchment paper. Cool dough, cut into 3 rectangles.
For the filling, beat butter with powdered sugar until creamy. Beat egg yolks with sugar in hot water bath until creamy, continue beating without water bath until cooled.
Stir in yogurt, rum and rusk crumbs, fold the mixture into the whipped butter. Spread on 2 sponge cake layers and place on top of each other. Place uncoated base on top. Cool, then cut into triangles.
Mix red wine, egg white and powdered sugar to make a glaze and coat the triangles.
Our tip: Use high-quality red wine for an especially fine taste!