A "roux" is a key component in one of the 5 "mother sauces" of French cooking: the Sauce Béchamel:
Paul Prudhomme on how to make a Roux:
Bechamel Sauce uses milk as its base liquid to make a white sauce. But what happens if you use shrimp, chicken, beef, or vegetable stock? You quickly end up with a tasty gravy!
The principles of these sauces combine a fat, a thickener, and a stock. You can change up any of these to make a wide combination of flavors. How might a switch in any or all of these ingredients represent cultural, economic, historical, or ecological forces?
What is the "trinity?" and what can we learn from it?
Here John Besh makes a gumbo that starts with a "trinity" - even if he is using a Zatarain's mix!