Make sure the butter is at room temperature before you start.

Mix it with sugar, brown sugar, and vanilla sugar until it forms a homogeneous mass. Ideally, use a stand mixer, it takes a few minutes.

Add the egg while still mixing.

Mix all the dry ingredients in a separate bowl and add them to the mixture while still stirring.

Finally, fold the chocolate into the dough and mix well.

Let the dough rest for a couple of hours if possible.

Line a baking tray with parchment paper and place dough portions of about 40 grams each evenly spaced on the tray.

Bake them for 15 minutes at 170 degrees Celsius (338 degrees Fahrenheit) in a conventional oven.

Let them cool for 10 minutes before serving.

If they are not all eaten immediately, store them in a container with a piece of parchment paper between the lid and the container.