Stir together milk chocolate chips and peanut butter chips.

Coarsely chop 1-1/3 cups chip mixture in food processor or by hand; place in medium bowl.

Place remaining 2/3 cup chip mixture and shortening in small microwave-safe bowl.

Microwave at HIGH (100%) 45 seconds; stir. If necessary, microwave at HIGH an additional 15 seconds at a time, stirring after each heating, until chips are melted and mixture is smooth.

Pour melted chocolate mixture over chopped chips; stir to coat evenly.

With hands, form mixture into 1-inch balls.

Place in small candy cups, if desired.

Store in cool, dry place.