This is a basic, classic sauce that every fish and seafood cook should have under his or her belt. It is a variation on a sauce veloute (Vel-oo-TAY), which is an enriched roux. Sounding too French? Bear with me, as this is a quick and easy -- and delicious -- sauce for simply prepared fish.
2 T. flour
2 T. butter (or oil)
1/2 cup white wine
1 cup fish stock
When you have finished pan-frying or sauteing your fish or seafood, add 2 more tablespoons of whatever oil or butter you cooked the fish with, scraping any browned bits off the bottom of the pan with a wooden spoon.
Turn the heat to medium-low and sprinkle in the flour and mix well with a fork or wooden spoon. Let this cook, stirring often, until it turns light brown; you are making a roux (pronounced "roo" in case you were wondering). It is very important not to burn this!
When the roux is light brown, add the wine. It will sputter. Mix well and scrape any browned bits off the bottom with the wooden spoon. This is important, so get them all.
It may thicken up quite a bit immediately, so add the stock and mix well. Bring this to a boil over high heat.
A word on the stock. Use appropriate stock for your dish, i.e., shrimp stock for shrimp, lobster stock for lobster, fish stock for fish. You can always sub in another stock if you need to, but adding the right stock makes your whole dish one step better. (instructions on how to make stock are below).
When the sauce has reduced by about half, taste a bit for salt and add more if you need to.
The sauce is done when it can coat the back of a spoon, or when it takes a second or so to fill in after you drag the wooden spoon through the center of the pan. If you really want to get fancy, pour the sauce through a fine-mesh strainer before serving.