Line a 9-in. square pan with foil and grease the foil with 1 tablespoon butter; set aside. In a heavy saucepan, combine the sugar, milk, marshmallow creme and 1/4 cup butter. Cook and stir over medium heat until sugar is dissolved. Bring to a rapid boil; boil for 5 minutes, stirring constantly. Remove from the heat.
Pour 3 cups of hot mixture into a bowl; add 1 cup peanut butter chips. Stir until chips are melted and mixture is smooth. Pour into prepared pan.
To the remaining hot mixture, add cocoa, vanilla, and remaining chips and butter; stir until chips and butter are melted and mixture is smooth. Pour evenly over peanut butter layer in pan. Cool. Using foil, lift fudge out of pan. Cut into 1-in. squares. Refrigerate in airtight containers.Yield: 3-1/2 pounds.