Bake 35 to 38 minutes or until toothpick inserted 2 inches from side of pan comes out almost clean. Cool 30 minutes; top with remaining peanut butter cup halves. In small microwavable bowl, add hot fudge topping. Microwave uncovered on High 15 to 20 seconds, and drizzle on top of brownies. Cool completely, about 1 1/2 hours.