Heat chocolate and peanut butter in microwave on medium for 2-4 minutes. Stir until smooth. Pour onto a foil-lined baking sheet sprayed with nonstick cooking spray. Spread into a thin layer. In another bowl, melt chocolate chips until smooth - 30 seconds, to 1 minute. swirl over peanut butter layer, and with a knife, marbleize (drag knife through both layers in one direction, and then turn the pan 1/4 turn and drag the knife through again). Freeze for 5 minutes or refrigerate for 10, until set. Break into bite-sized pieces.
