Prepare a landing zone for the sauce. Cover a sheet tray with plastic wrap or have mason jars ready.
In a medium saucepan with high sides, combine light brown sugar and water. Stir to hydrate all the sugar. Then, add the light corn syrup.
Cook the sugar mixture on a medium heat. Allow the caramel to come to a boil before you disturb it. Once it has come to a boil, place the candy thermometer in the caramel.
Continue to cook until soft ball stage 234°F or 112°C.
Once it has reached the soft ball stage, place the pot on a kitchen towel. Whisk in the butter until completely combined, followed by the heavy whipping cream and salt. Stir until the salt is dissolved and simmer until a cohesive sauce is formed.
Continue to simmer the sauce for 1-2 more minutes to achieve a thicker consistency and ensure it is emulsified.
Pour into the prepared sheet tray or heat-safe bowl. Allow to cool at room temperature before moving to the refrigerator.
Notes
Yield – 2 cups Technique – Test your thermometer before making the caramel. You can test with boiling water. Leave the thermometer in the water for a few seconds. It should read 212°F or 100°CVariations—Light or dark brown sugar will work for this sauce. Dark brown sugar gives the sauce a deeper, more molasses flavor. Storage – Place cooled butterscotch sauce in an air-tight container or mason jar. Store it in the refrigerator for up to 2 months.