In a microwave or double boiler, melt chocolate chips and shortening. Chill for 15-20 minutes or until thickened.
Meanwhile, line a 9-in. square pan with foil; grease the foil and set pan aside. In a heavy saucepan over low heat, melt butter. Stir in marshmallows and butterscotch chips until melted and smooth.
Place the popcorn in a large bowl; add marshmallow mixture and toss until coated. Firmly press half of the popcorn mixture into prepared pan. Spread chocolate mixture evenly over popcorn. Firmly press remaining popcorn mixture over chocolate.
Chill for 30 minutes. Lift out of pan, using foil edges. Remove foil; cut into bars. Yield: 2 dozen.