Heat the chocolate syrup in a microwave-safe bowl for about 1 minute. Stir in the peanut butter until smooth; set aside.
Layer half of the ice cream sandwiches on the bottom of an 8x8 square baking dish. Evenly pour half of the chocolate-peanut butter sauce over the top. Spread with an even layer of half of the COOL WHIP, then sprinkle with half of the peanut butter cups. Repeat the layers (sandwiches, chocolate sauce, COOL WHIP) ending with another sprinkle of peanut butter cups. Cover loosely with foil and freeze for at least 1 hour. To serve, cut into squares.
*Note: This recipe can be doubled, using a 9x13-inch pan.