Pop corn in microwave following directions - discarding unpopped kernels.
Butter 9 x 12 x 2 inch microwave dish. Set aside.
Measure and mix butter, shortening and chocolate chips in bowl. Microwave Uncovered on High (100%) until chips are softened and mixture becomes smooth when stirred - about 2 1/2 minutes.
Stir in marshmallows. Microwave uncovered until they are almost melted - 15 to 20 seconds.
Stir in peanuts and popcorn until evenly covered with mixture. When cool, press in pan with spoon. Refrigerate until firm - about 1 hour. Cut in squares.
