This is a basic, classic sauce that every fish and seafood home cook should have under his or her belt. It is a variation on a sauce veloute (vel-oo-tay), which is an enriched roux. If the sauce is sounding too french or complicated, don't let that scare you off. This is a quick, easy, and delicious sauce for simply prepared fish. When cooking with fish stock it's important to use the 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. Fish stock can be found in most grocery stores or even specialty fish stores. It's also quite easy to make your own. Ask your fishmonger for fish heads or parts for a stock. They are usually inexpensive. Simmer the fish parts with water and aromatics (celery, carrots, onions, etc. ) and you'll have a fish stock Super easy and worth the time. If you have leftover stock, just cool it and freeze it for next time you need it.