Mix sour cream, vanillin sugar, eggs, sugar and sauce powder. Sort blueberries. Roll out the dough on baking paper and line a small baking tray with it. Spread dough with jam and sprinkle with blueberries. Pour over the top and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 20 minutes.
Sprinkle almond flakes onto the cake about 3 minutes before the end of the baking time. Take the cake out of the oven and let it cool down on a cake rack. Sprinkle with icing sugar before serving