Line 20 cups of a mini-muffin tin with mini paper baking cups.
In a microwave-safe bowl, melt the chocolate chips in the microwave (about 2 minutes). Stir; continue to microwave in short-bursts until completely melted and smooth. With a small spoon, scoop the chocolate into the bottom of each cup. Refrigerate.
Meanwhile, in a medium bowl- combine the peanut butter and the powdered sugar with a sturdy spoon. Roll teaspoonfuls of the peanut butter mixture into little balls. Flatten the balls and place them on top of the 1st layer of chocolate. Top with more melted chocolate and refrigerate to set.
Peel and eat. These may be kept refrigerated or at room temperature.