Combine peanut butter, marshmallow creme, and vanilla on a large bowl and set aside. Combine sugar, milk, and salt. Stir well. Cook over medium heat until mixture comes to a boil. Boil 4 minutes. Stir occasionally. Remove from heat and pour over peanut butter mixture. Stir quickly until well blended. Pour into a buttered 13 x 9 x 2 inch pan. Allow candy to cool at least 2 hours. Cut into squares. Yield: 3 1/2 dozen.