Sift the flour and mix with the baking powder. Beat the butter with salt, sugar and vanilla sugar until frothy. Stir in the egg. Gradually add the flour. Finally, knead the oat flakes and chocolate chips into the dough.
Now let the finished cookie dough rest in the refrigerator for half an hour covered with foil. Use a teaspoon to mark small piles of dough and place them on a baking sheet lined with baking paper with a gap (at least 3 cm on all sides).
Bake in the preheated oven at 175 ° C (gas: level 2, convection: 160 ° C) for approx. 15 - 20 minutes until golden yellow. Then let the cookies cool down on a wire rack and store them in a well-closing biscuit tin after cooling.