Line a 9x9-inch pan with aluminum foil, and set aside.
Melt 5 tablespoons butter in a large microwave-safe bowl. Stir in peanut butter, brown sugar, and powdered sugar. Press the peanut butter mixture into the prepared pan, and chill.
Melt the remaining 5 tablespoons butter and the chocolate chips in a microwave-safe bowl in microwave for 1 minute. Stir, heat in 30-second increments until smooth. Pour over the peanut butter mixture.