1Heat oven to 350°F. Lightly spray 13x9-inch pan with baking spray with flour (do not use dark or nonstick pan). In large bowl, mix cake mix, butter, milk and 1 egg with spoon until dough forms. Spoon into pan. Place plastic wrap on dough; press evenly in pan. Remove plastic wrap. Sprinkle dough with peanut butter chips and peanuts.
2In large bowl, beat cream cheese, peanut butter, vanilla and 3 eggs with electric mixer on medium speed until smooth. Beat in powdered sugar on low speed. Pour mixture over chocolate mixture in pan; spread evenly.
3Bake 45 to 50 minutes or until topping is set and deep golden brown. Cool at least 30 minutes to serve warm, or cool completely. When cutting serving pieces, wipe knife with paper towel after cutting each row. Top each piece with hot fudge topping and chopped peanuts. Store covered in refrigerator.