1 . Stage
Preheat the oven to 175 degrees. Put the baking sheet on parchment paper. Using a mixer, combine the butter and sugar, whisking until light, fluffy. Add the eggs one at a time, then add the cocoa powder.
2 . Stage
Add flour, salt and baking powder. Add pieces of chocolate and mix gently.
3 . Stage
The dough will be very thick. Knead it lightly with your hands and divide into 12 parts. Roll each part of the dough into a ball and slightly press down. If desired, decorate the top with drops of chocolate.
4 . Stage
Put cookies on a baking sheet and bake for 20 minutes. Allow to cool on a baking sheet for 5 minutes, then cool completely on a wire rack.