In a bowl take butter and sugar..... mix it untill become fluffy add vanila extract baking soda baking powder coca powder milk...mix ingridents well.make dough.... dont over knead....take lemon sized dough. Place a ball of dough in the palm of your hand and flatten it well. Place dark chocalate piece in the center and fold the edges of the dough over, using your fingers to pinch them together and shape the dough around thechocalate piece...... bake it in preheated oven for 15 to 20 min at 180°c