Mix flour, milk, eggs, salt, sugar and mineral water to a dough and let it rest for about 15 minutes.
Mix sugar and cinnamon powder.
For the sauce, mix cornstarch and vanilla sugar with a little three tablespoons of the milk until smooth.
Bring remaining milk to a boil, stir in mixed amount, bring to a boil again and set aside.
Peel the apples, cut out the core and slice the apples.
Heat fat in a frying pan. Pull apple slices through the batter in batches and fry over medium heat until golden brown on both sides.
Drain on paper towels, sprinkle with cinnamon-sugar while still hot and serve with the sauce.