Line 13x9-inch pan with foil, with ends of foil extending over sides.
Place graham wafers in prepared pan, cutting as necessary to completely cover bottom of pan.
Microwave semi-sweet chocolate and peanut butter in medium microwaveable bowl on HIGH 1-1/2 to 2 min. or until chocolate is completely melted and mixture is well blended, stirring every 30 sec.
Pour over graham wafers; spread to completely cover wafers.
Melt white chocolate as directed on package.
Drop spoonfuls over semi-sweet chocolate; swirl gently with knife.
Refrigerate 1 hour or until firm.
Use foil handles to lift dessert from pan; peel off foil.