And straight-reduced cream makes such an excellent base for a sauce. It will not break like half-and-half or milk can. It does not need flour to bind it so a roux is not necessary. (E.g., in Jane's recipe above the wine could be mixed with the broth at the outset, reduced to just a few tablespoons (skipping the butter and flour) and then added to cream that you've been reducing alongside. The flavor and finish are richer (but, without the flour or butter, 'lighter' in a way) than a typical white sauce, with a cleaner flavor. Though a roux-based white sauce can often be preferable to a cream reduction, for something as rich and tasty as a tenderloin a cream reduction is a winner, imo.
The cream can be reduced partially, halfway, a bit more than that, or all the way ahead of time. Cream reductions can also be finished ahead of time and reheated later. It is often best not to let the sauce thicken as much as you normally might when you first make it if the plan is to reheat later.
If the sauce includes cheese do not let the sauce boil when making it or during the reheat. If you make the sauce earlier in the day you can hold it for quite a while (negating the need to reheat) if you pour it into a pre-heated coffee or lunch thermos.