Mix the starch and 3-4 tablespoons of juice. Put the rest of the juice and 50 g sugar in a pot and bring to the boil. Remove from the heat, stir in the starch and bring to the boil again. Add frozen berries, defrost and carefully stir in. Let cool down.
Separate eggs. Cream fat, egg yolk, remaining sugar, salt and vanillin sugar with the whisk of the hand mixer. Add lemon zest, lemon juice, mascarpone, quark, milk and pudding powder and stir in. Beat the egg whites until stiff and fold into the mascarpone and quark mixture. Grease an oven dish (20 x 29 cm; 1 1/4 litre capacity). Pour some of the mascarpone mixture into the baking dish and spread it. Place 3 lasagne plates on top. Spread half of the berry compote on top. Pour half of the mascarpone mixture over it and smooth it down. Place the remaining lasagne sheets on top.
Place 3 lasagne plates on top. Spread half of the berry compote on top. Pour half of the mascarpone mixture over it and smooth it down. Place the remaining lasagne sheets on top. Layer the remaining berry compote and mascarpone mass on top and bake in a preheated oven (electric: 200 °C/ gas: level 3) for 40-45 minutes. Sprinkle almond flakes on the lasagne about 15 minutes before the end of the cooking time. Serve dusted with icing sugar