Line a 9x13 baking pan with foil. Grease all sides of the foil with butter or nonstick baking spray. In a large, heavy bottom sauce pan add sugars and milk and stir to combine. Oven medium low heat, stirring occasionally, bring mixture to a full boil. Boil for three minutes without stirring. Remove from heat and quickly add peanut butter, marshmallow crème and vanilla. Beat until smooth. Pour in prepared pan. Allow to cool completely. Cut in squares.