In a microwave, melt chocolate chips and shortening; stir until smooth. Place a scant teaspoonful inside each foil cup and rotate it gently in the palm of your hand to coat the sides and bottom. (Use a spoon to help coat the sides if necessary.)
Place cups in miniature muffin pans; chill until firm. Set remaining chocolate aside. In a medium bowl, combine the peanut butter, milk powder, corn syrup and vanilla until smooth.
Shape into 1-in. balls; press one ball into each chocolate cup. Top with remaining melted chocolate. Chill until set. Store in an airtight container in refrigerator.