Step 1

Heat oven to 350ºF.

Step 2

Line 13x9-inch pan with foil, with ends of foil extending over sides. Spray with cooking spray; set aside. Microwave butter, unsweetened chocolate and 2 oz. semi-sweet chocolate in microwaveable bowl on HIGH 1-1/2 to 2 min. or until butter is completely melted, stirring after 1 min.; stir until chocolate is completely melted and mixture is well blended.

Step 3

Mix 1-1/2 cups sugar, eggs and 1 tsp. vanilla in large bowl. Stir in chocolate mixture, flour and 1/2 cup nuts until blended; spread into prepared pan.

Step 4

Bake for 25 to 30 min. or until toothpick inserted in center comes out with fudgy crumbs. (Do not overbake.) Cool completely in pan on wire rack.

Step 5

Beat cream cheese, remaining sugar and remaining vanilla until creamy; stir in remaining nuts. Spread over brownies. Melt remaining semi-sweet chocolate; drizzle over icing. Swirl gently with knife. Use foil handles to lift brownies from pan before cutting into squares.