The best way to reheat cream-based sauces is to work slowly and add additional cream as you go (via Sheet). First bring the sauce to room temperature, then pour it into a saucepan and gradually raise the temperature of the fire while adding the cream little by little. The fat in the cream helps keep the sauce from separating. If it separates, remove it from the heat and add a teaspoon of cold water. Be sure to stir vigorously and the sauce should start to replenish.
According Pantry and pantry, a double boiler is one of the best methods because the secondary heat keeps the sauce from getting too hot too quickly. A regular saucepan puts the pasta sauce in direct contact with the heat source, and you might get inconsistent results depending on the type of saucepan you use. A double boiler will provide consistent results and give you better control over the process. Reheating cream-based sauces on the stovetop will give better results than using a microwave, but you can still use it in a pinch. Use a low setting and microwave the sauce in 20 second increments, checking and stirring as you go.
With a little patience, you can extend your sauces an extra night – but the white sauce is meant to be eaten fresh, so make small amounts and try to avoid having any leftovers at all. If not, one of these methods is sure to save it.