Chop the butter and chocolate and melt it in the microwave until it's smooth. Heat the chocolate carefully by checking and mixing it often.
Blend eggs with sugar until it has tripled in quantity and the liquid is pretty thick; about 15 minutes. In small portions, mix in chocolate (room temperature) into the eggs, add vanilla extract, mix well.
Sift flour. Add salt and baking powder and mix it up. In small amounts, add your flour mixture to egg mixture. Cover up the bowl and let it sit in a refrigerator for at least 4 hours, you can even leave it overnight. The dough should turn out with a pretty hard texture.
Out of dough, make a small sound shape. Make sure to work quick with cold dough, otherwise, it will become sticky and you will need to put it back into the fridge. Dip the cookie into powdered sugar.
Bake them at 350 °F degrees for 12-20 minutes, until the outside has a hard shell, but inside still feels soft, all depending on the size of the cookie I would suggest checking on them after 12 minutes. (Don't overbake the cookies or they will come out dry)