Every kid's favorite combination.
In large shallow glass baking dish, microwave butter on HIGH until melted, about 1-1/2 minutes. Stir in sugar, corn syrup and grape juice concentrate. Microwave on HIGH until mixture boils, about 3 minutes, stirring once. Microwave on HIGH 3 to 4 minutes without stirring. Stir in popped popcorn. Microwave on 75% POWER about 6 minutes, stirring every 2 minutes to coat popcorn evenly. Immediately upon removing from microwave, sprinkle peanut butter pieces over top of popcorn. Do not stir. Cool completely. Break apart and store in tightly covered container.
Recipe compliments of The Popcorn Board