NYT Cooking: Most cooks agree that gumbos must have the vegetable trinity of chopped bell pepper, onion and celery, and that they should be highly seasoned. Some gumbos do contain sausage, shrimp and chicken, but there are humbler ones that are made with only salt pork, onions and greens. Finally, there is the filé powder camp. These cooks use copious amounts of the stuff, which is...
