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  1. In a heavy pot (6-quart or larger) over medium heat, combine the sugars and butter and cook just until the sugar is melted. Raise the heat to medium-high, and add the vanilla bean.

  2. Add the cream in four additions, bringing the sauce to a simmer and allowing it to partially reduce before adding more (about 4 to 6 minutes). Stir the mixture as necessary to keep it from boiling over.

  3. Once all the cream is added and the sauce thickens slightly (it should just begin to fall in a sheet from the spoon), remove from the heat and add the salts and vanilla. Cool completely before using.

  4. Butterscotch sauce will keep in the refrigerator for up to 6 months.