If using frozen berries, unfrozen them in advance and dry them from fluid.
2
Separate egg yolks from egg whites. Using hand mixer beat egg whites with sugar and add yolks one by one. Add vanilla sugar and vanilla extract and then milk, oil, sour cream, flour and baking powder until all ingredients are well mixed.
3
Put baking sheet onto baking tray ( baking tray size: approx 25 x 25) and pour 2/3 of the mixture. In the preheated oven bake it on 180C for 10min, then take it out and put evenly berries and add the rest of the mixture on top of it.
4
Bake for another 30-40 minutes until the surface turns golden yellow to slightly brownish. Take out, let it cool down and sprinkle with powder sugar. You can eat it warm or cold over next days. You can serve it with fresh cream if you like.