1. Place sugar in a heavy skillet over medium high heat. Let stand 2 minutes or until sugar starts to melt. Stir with a heat proof spatula. Cook 3 more minutes or until sugar is melted and an amber color. Watch closely as the difference between burnt caramel and perfect caramel is seconds. Add butter, salt and vanilla, whisking thoroughly. Mixture will bubble vigorously. Once smooth, add cream, whisking until smooth. Remove from heat. Pour into glass container. Caramel thickens as it cools. Yields about 1 cup.