Combine the sugar, corn syrup and water in a medium heavy saucepan. Cook over medium-high heat, stirring constantly, until the sugar dissolves and the syrup is bubbly. Stop stirring completely and let boil undisturbed until the mixture turns amber, and a candy thermometer reads 380 degrees. Immediately remove saucepan from heat. Slowly add the warmed cream to the mixture. It should bubble like crazy.

Use a wooden spoon and stir the mixture, making sure to scrape up the thicker part on the bottom of the saucepan, until it's smooth. (If the sauce becomes lumpy, return it to the stovetop and heat until they dissolve.)  Add the butter and stir. It's okay if it's a little streaky. Let the sauce cool for 3 minutes then gently stir in the vanilla