Preheat oven to 350F. Line 13x9-inch baking pan with foil, with ends of foil extending over sides of pan; grease foil lightly. Set aside. Microwave unsweetened chocolate and butter in large microwaveable bowl on HIGH 2 min. or until butter is melted; stir until chocolate is completely melted. Stir in sugar.
Add all remaining ingredients except white chocolate; mix well.
Pour into prepared pan.
Bake 30 to 35 min. or until wooden toothpick inserted in center comes out with fudgy crumbs. (Do not overbake.) Cool in pan. Lift dessert from pan onto cutting board, using foil handles.
Cut into 24 brownies.
Melt white chocolate as directed on package. Spoon into small plastic bag.
Roll up bag to push chocolate into bottom of bag.
Cut off tiny piece from one of the bottom corners of bag. Twist top of bag, then gently squeeze from top of bag to drizzle chocolate over brownies in a spiderweb design.
