In a saucepan over low heat, melt chocolate and butter. Transfer to a bowl; add corn syrup, vanilla, 2 cups confectioners' sugar and milk powder. Mix well.
Place remaining sugar on a clean surface; place dough on the surface and knead sugar into the dough until all of it is absorbed. Shape teaspoonfuls into 2-in. logs; wrap in waxed paper and twist ends. Refrigerate until firm.