1½– 2teaspoons good quality sea salt or kosher salt
Have all your ingredients measured and ready to go before starting this recipe. Combine the sugar and water in a large, deep, heavy saucepan and place over medium-high heat. Once the sugar starts to liquefy, whisk it vigorously and continue whisking until it starts to boil. Stop whisking as soon as it starts to boil. Continue to boil the sugar until it becomes a deep amber color, like an old penny. As the sugar caramelizes, gently swirl the pan now and again to ensure even caramelization.
Take the pan off the heat and quickly whisk in the butter. Carefully add the cream slowly while whisking. (The mixture will expand considerably and may bubble and spurt, so stand back while doing this or wear an oven mitt.) Stir in the salt. Let the mixture cool in the pan for 10 minutes then pour into a glass jar with a lid. Let cool completely and store, covered, in the refrigerator for up to 2 weeks.
To reheat the sauce for serving, remove the lid from the jar and microwave for a few seconds or remove the lid from the jar and place the jar in a pan of simmering water until warm.