In Double Boiler, melt chocolate chips with milk. Beat with mixer one yolk at a time into the melted chocolate. Remove the pan from heat and start adding the butter pieces a few pieces at a time using the mixer. Beat 2-3 minutes, then mix in the vanilla. Chill the chocolate in the refrigerator. When the chocolate is workable, roll into balls the size of marbles and roll in the chocolate shot or ground nuts. Serve well chilled in tiny paper/foil cups. Keep the Truffles refrigerated. Makes approximately 50 Chocolate Truffles.