1. In a large frying pan or Dutch oven, heat the oil over moderate heat until almost smoking. Add the flour and whisk until it's the color of peanut butter, about 3 minutes. Whisk in the broth and continue whisking until the sauce starts to thicken, about 2 minutes.
2. Stir in the bell pepper, celery, onions, bay leaf, salt, cayenne, black pepper, and thyme. Bring to a simmer, cover, and cook over low heat until the vegetables are tender, about 15 minutes.
3. Add the shrimp and scallions and simmer until the shrimp are just done, about 3 minutes. Serve the étouffée over the rice.
Fish Alternatives: The most authentic substitution, if you can get them, would be cooked crawfish tails. Toss them in at the end and just heat through.
Wine Recommendation: The down-home taste of this American original is perfect with a refreshing American white wine. Try a pinot gris from Oregon or a dry riesling, either from Oregon or Washington State. All of these have more acidity than their California counterparts.