One can get finicky with pan sauces. (I, for one, am guilty of this.) Various thickening agents, aromatics, and even cream all bring certain charms to the pan, but my favourite (and incidentally easiest) pan sauce to make is mostly butter.
Not every sauce needs to have the viscosity of a gravy. In fact, when serving a nice steak or piece of expensive seafood, you don’t necessarily want a thick, crazy-flavorful sauce. You want an accent. Melted butter adds richness and luxury, but it doesn’t pull focus. Butter is not a great deglazing agent, however, which is why I say my favourite pan sauce is mostly—but not entirely—melted butter. The other ingredient in my favourite pan sauce is wine (red or white, depending on the protein).
The wine is needed for getting all those browned bits—known to fancy folks as “fond”—unstuck from the pan so that they may rejoin the rest of the dish. Exactly how much wine you add depends on the size of your pan and how much food you cooked, but I usually add enough to just cover the entire surface area of the pan, scrape all the bits up with a wooden spoon, then let the wine reduce until it’s opaque and kind of murky looking. Add many tablespoons of butter (at least three), swirl that around with wine, and let it foam and sputter until it’s just golden. Pour all over your prepared protein, and enjoy.