1. Cover a baking sheet with wax paper, and spray paper with nonstick cooking spray. Melt milk chocolate in a small saucepan over low heat, stirring constantly. Stir in the cream and vanilla. Spoon tablespoon-sized scoops of the chocolate mixture onto the prepared baking sheets. Refrigerate until well chilled, about 30 minutes.
2. Melt the chocolate chips in a small saucepan over low heat. Stir in shortening.
3. Roll each piece of chilled chocolate into a ball. Use a spoon to dip chocolate balls into the melted chocolate chip mixture. Return truffles to baking sheet, and chill until firm.