LINE baking sheet with wax paper.
PLACE milk chocolate and semi-sweet morsels in large mixer bowl. Heat cream to a gentle boil in small saucepan; pour over morsels. Let stand for 1 minute; stir until smooth. Stir in peppermint extract. Cover with plastic wrap; refrigerate for 35 to 45 minutes or until slightly thickened. Stir just until color lightens slightly. (Do not over mix or truffles will be grainy.)
DROP by rounded teaspoonfuls onto prepared baking sheet; refrigerate for 10 to 15 minutes. Shape into balls; roll in walnuts. Store in airtight container in refrigerator.
After rolling chocolate mixture into balls, freeze for 30 to 40 minutes. Microwave 1 3/4 cups (11.5-oz. pkg.) NESTLÉ TOLL HOUSE Milk Chocolate Morsels and 3 tablespoons vegetable shortening in medium, uncovered, microwave-safe bowl on MEDIUM-HIGH (70%) power; STIR. Morsels may retain some of their original shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until melted. Dip truffles into chocolate mixture; shake off excess. Place on foil-lined baking sheets. Refrigerate for 15 to 20 minutes or until set. Store in airtight container in refrigerator.