Shrimp Etouffee

To make a roux, whisk together oil and flour in a large heavy saucepan (cast iron is perfect, but any heavy-bottomed pot or pan will do) over medium to medium-low heat. Once combined, it is easier to use a wooden spoon to stir. Stir continuously for at least 20 minutes, until mixture turns a dark caramel color. It should darken very slowly. If it darkens too fast, turn down the heat. The roux will burn if the heat is too high or you don't stir continuously. Be sure to really stir all the way up to the edges of the pot. You don't want any of the mixture to stay in one spot for too long.

Turn heat to low and add onion, green pepper, and celery to roux. It will start to sizzle loudly and darken some in color. Cook 5 minutes, or until vegetables are soft.