Here’s the 1993 recipe for Redenbacher’s Ribbon O’ Fudge Bars:

4 cups miniature marshmallows
1 cup butterscotch chips
3 tbsp. butter
3 qts. Popped Orville Redenbacher’s Gourmet Original Popping Corn, unpopped kernels discarded
1 (12-oz.) hot fudge sauce

In large Dutch oven over low heat, melt marshmallows with butterscotch chips and butter; stir occasionally until smooth. Add popcorn; toss until well coated. Press half of mixture firmly into a greased 9-inch square pan. Spread fudge sauce evenly over mixture. Press remaining popcorn mixture over fudge. Allow mixture to cool and harden. Slide spatula under entire mixture and slide into cutting board to cut into bars. Makes 16 bars.

I found this retro recipe at http://pzrservices.typepad.com/vintagerecipes.