1Cover cookie sheet with aluminum foil. Melt baking chocolate in heavy 2-quart saucepan over low heat, stirring constantly; remove from heat. Stir in butter until melted; stir in whipping cream. Refrigerate 10 to 15 minutes, stirring frequently, just until thick enough to hold a shape.
2Drop mixture by teaspoonfuls onto cookie sheet. Shape into balls. (If mixture is too sticky, refrigerate until firm enough to shape.) Freeze 30 minutes.
3Heat shortening and chocolate chips over low heat, stirring constantly, until chocolate is melted and mixture is smooth; remove from heat. Dip truffles, one at a time, into chocolate. Place on aluminum foil-covered cookie sheet. Immediately sprinkle some of the truffles with finely chopped nuts or decorating candies.
4Refrigerate truffles about 10 minutes or until coating is set. Drizzle some of the truffles with mixture of 1/4 cup powdered sugar and 1/2 teaspoon milk. Refrigerate just until set. Serve at room temperature. Store in airtight container.