Separate the eggs. Mix the butter with the sugar until frothy. Gradually add the egg yolks. Stir in the slightly drained low-fat quark, mascarpone and pudding powder. Beat the egg whites until stiff and fold them with the cornstarch into the mascarpone / quark mixture. Heat the oven to 180 degrees. Grease a 28 cm springform pan with butter and sprinkle with breadcrumbs. Pour in the mascarpone / quark mass and smooth it out. Bake until golden in about 60 minutes.