Microwave chocolate and butter in large microwaveable bowl on HIGH 1 to 1-1/2 min. or until chocolate is almost melted. Stir with whisk until chocolate is completely melted. Stir in powdered sugar. Blend in whole eggs and egg yolks. Stir in flour; set aside.
Mix cream cheese, peanut butter, brown sugar and vanilla until well blended.
Pour half the chocolate batter into 1-qt. souffle dish sprayed with cooking spray; cover with layers of cream cheese mixture and remaining chocolate batter.
Bake 20 min. or until edge is set but center is still slightly soft. Cool slightly.