Mix the milk, sugar, vanilla sugar, salt, eggs and butter together and then stir in the flour (makes 500 ml dough).
Heat the blueberries with juice in a saucepan, add sweetener if necessary, mix the cornstarch with a little water, thicken the blueberries with it and keep warm.
Heat 10 g butter and 1 teaspoon rapeseed oil in a non-stick pan, add 125 ml of batter, bake until light brown while turning, remove and keep warm. Bake another 3 pancakes with the rest of the batter.