You can make caramel sauce with just sugar and cream–and it will be wonderful. Those two ingredients are all you need to make an excellent topping for ice cream, or for a sauce poured over slices of cake, pie, or profiteroles. However, if you are going to swirl caramel sauce into ice cream (as I will be doing, right here, very soon) you’ll want to have a slightly higher ration of cream to sugar, and (who can complain) some butter! The added richness of the extra cream and butter assures that the caramel sauce will not seize up and become hard and sticky when frozen. I like this buttery caramel sauce so much that I use it for both swirling into and pouring over ice cream–and just about everything else.
Caramel sauce needs to be stored in the refrigerator, and it will become firmer once it is cold. While this sauce stays soft enough that you can easily spoon it out of the jar when cold, it tastes much better if you warm it up. I recommend warming the sauce (still in its jar) in a water bath on top of the stove. You can also warm it in a microwave oven. If you are using it for a sauce, get it quite warm. If you are folding it into ice cream, get it just warm enough to pour.
Strain into a heatproof jar.