Line a 9-inch square baking pan with foil; grease foil with the 2 teaspoons butter. Set aside. In a large heavy saucepan, combine milk, sugar, and remaining butter. Cook and stir over medium heat until sugar is dissolved. Bring to a rapid boil; boil for 5 minutes, stirring constantly. Remove from heat; stir in chocolate chips and marshmallow creme until melted. Fold in caramels, cashews, and vanilla; mix well. Pour into prepared pan. Cool. Remove from the pan and cut into 1-inch squares. Store at room temperature.