Preheat oven to 350° F. Beat 6 tablespoons softened butter in large mixer bowl until creamy; beat in sweetened condensed milk, 1 grated tablet Abuelita chocolate, egg and flour until smooth dough forms. Refrigerate for 10 minutes.
Reserve a quarter of the dough and make balls and bones for the cookies. Form cookie balls with the remaining dough. Place a couple of bones on each of the cookie balls and then a smaller ball on top of the bones. Place on baking sheets.
Bake for 15 minutes; brush cookies with the melted butter and coat with remaining tablet of grated Abuelita chocolate. Let cool completely.