Preheat the oven to 190 ° C (top / bottom heat). Mix the butter and sugar in a bowl until creamy, then add the egg yolks. Add the flour with the cocoa powder, a pinch of salt and the nuts. Mix everything well.
Shape the dough into small balls (about the size of a walnut) and place on the baking tray lined with baking paper. Then use the handle of a wooden spoon or something similar to press a recess in the center of the ball.
Bake the cookies in the oven for about 12-15 minutes. Let the cookies cool down and fill the cavity with the nougat (if necessary, heat the nougat slightly).