Over medium low heat, mix the sugar, half-and-half, butter and salt in a saucepan.
Cook while whisking gently for 5 to 7 minutes, until it gets thicker.
Add the vanilla and cook another minute to thicken further.
Remove from heat, let cool slightly then pour the sauce into a jar. Refrigerate until cold, at least 10 minutes.
Notes
The nutritional value is approximately per tablespoon.StorageFridge: Store in an airtight container in the fridge for up to 3 weeks. Freezer: Store in an airtight container in the freezer for up to 3 months.SubstitutionsButter: You can use unsalted butter, just add another 1/4 teaspoon of salt.