2
Spray bottom and side of 9-inch springform pan with cooking spray; dust side with 2 tsp. sugar.
3
Beat egg whites in small bowl with mixer on high speed until stiff peaks form; set aside. Microwave semi-sweet chocolate and butter in large microwaveable bowl on HIGH 1-1/2 min. or until chocolate is completely melted and mixture is well blended, stirring every 45 sec. Stir in 1/2 cup of the remaining sugar. Add egg yolks, 1 at a time, stirring after each until blended. Stir in sour cream.
4
Add egg whites to chocolate mixture in batches, gently stirring after each until blended. Stir in nuts. Pour into prepared pan.
5
Bake 35 min. or until toothpick inserted in center comes out with fudgy crumbs. (Do not overbake.) Run knife around rim of pan to loosen cake; cool before removing rim.
6
Melt white chocolate as directed on package. Beat cream cheese and remaining sugar in large bowl with mixer until blended. Add white chocolate; mix well. Gently stir in COOL WHIP; spread over cake. Refrigerate 4 hours.