The difference if this recipe from the classic recipe of shortbread is existence of baking powder. Thanks baking powder shortbread is a very gentle and just melts in your mouth.

Here is my recipe for shortbread.

200 gram of butter,
80 gram of sugar,
20 gram of vanilla sugar,
300 gram of flour
1 teaspoon of baking powder.

Quickly make a dough, roll up to 3-4 mm and cut use your beloved forms.
Bake about 10-12 minutes use non-lubricated tray, with temperature about
180-200 C degrees.

You can also try to add to your dough grated nuts, or poppy seeds, or cocoa,
or replace the vanillin with a cinnamon.