Attention peanut butter lovers! Regular brownies are great, but Peanut Butter and Milk Chocolate Chip Brownie Bars are even better. Bake this crowd-pleasing dessert with REESE'S Peanut Butter Chips and HERSHEY'S Milk Chocolate Chips for a treat that will keep guests coming back for more.
Heat convection oven to 300°F (standard oven: 350°F). Lightly spray one 18x26-inch full sheet pan with vegetable cooking spray.
Mix together butter, sugar and 3/4 oz. (1-1/2 tablespoons) vanilla in 20 qt. bowl of mixer fitted with paddle attachment until creamy. Add 14 oz. (8 eggs), mixing until fully incorporated. Blend together flour, HERSHEY'S Cocoa, baking powder and salt in large bowl. Gradually add to egg mixture, mixing until well blended. Spread into prepared pan. Bake 20 minutes*.
Meanwhile, using wire whisk, stir together sweetened condensed milk, REESE'S Peanut Butter Sauce, remaining 7 oz. (4) eggs and remaining vanilla in 4-qt. pitcher or measuring cup. Pour evenly over hot brownie. Set aside 1-1/2 oz. (1/4 cup) HERSHEY'S Milk Chocolate Chips and 1-1/2 oz. (1/4 cup) REESE'S Peanut Butter Chips; sprinkle remaining chips over peanut butter mixture. Return to oven; continue baking 20 to 40 minutes* or until peanut butter layer is set and edges begin to brown. Cool completely in pan on wire rack.
Place reserved chips and shortening in medium microwave-safe bowl. Microwave on MEDIUM (50%) 30 seconds; stir. If necessary, microwave at MEDIUM an additional 15 seconds at a time, stirring after each heating, until chips are melted and mixture is smooth when stirred. Drizzle over top of bars. When drizzle is firm, cut into 2-inch bars. Store loosely covered at room temperature.
Step 3: If using convection oven, rotate sheet pan one-half turn (180°) after 10 minutes of baking.