Melt the chocolate in a double boiler. Beat the butter with the powdered sugar until creamy, stir in the egg yolks. First stir in the chocolate mixture, then the nuts and flour. Wrap the dough in foil and refrigerate for about 2 hours.
Then shape about 40 balls from it, place them on baking sheets lined with baking paper at least 4 cm apart and press in a cashew nut. Bake at 180 ° C for about 12-15 minutes.
Store in a tightly sealed tin, possibly with an apple wedge for the first two days, so that they become nice and tender.