1. Pour the low-flour and cocoa powder into the basin through a sieve, add powdered sugar, salt and vanilla extract; cut the butter into small pieces, put it in the greenhouse and soften it and put it in the basin
2. Mix well with a spatula, then knead repeatedly with your hands until the butter and flour are completely fused to form a smooth dough
3. Then slowly roll the dough into a cylindrical strip, wrap it in greased paper, and freeze it in the refrigerator for about 30-60 minutes.
4. Take out the frozen dough, dip it with a layer of coarse sugar, and then cut into small pieces about 1cm thick
5. Put it in a baking tray lined with greased paper, leaving a larger gap, put it in the middle of the preheated oven at 170 degrees, and bake for about 13-15 minutes
