Gumbo is a stew or soup originating in Louisiana, and found across the Gulf Coast of the United States and into the U.S. South. It consists primarily of a strong stock, meat and/or shellfish, a thickener, and the vegetable "holy trinity" of celery, bell peppers and onion. The soup is traditionally served over rice. A traditional lenten variety called gumbo z'herbes (from the French gumbo aux herbes), essentially a gumbo of smothered greens thickened with roux, also exists.
The stock is always as rich as possible, made with whatever complements the type of gumbo (seafood stock for seafood gumbo, chicken stock for chicken gumbo, etc.).
A typical gumbo contains one or more kinds of poultry, shellfish, and smoked pork. Poultry used is typically chicken, duck, or quail. Local shellfish such as the freshwater crawfish and crab and shrimp from the Gulf of Mexico are frequently used. Tasso and andouille provide a smoky flavor to the dish.
Gumbos can be broadly divided between the use of okra as a thickener, and recipes using filé powder in that role. Roux may be added to either, and nowadays it is quite common for roux to be the sole thickening agent itself. Mixing okra and filé is uncommon in Louisiana.
Another division in types of gumbo is between Creole and Cajun styles. Creole gumbos generally use a lighter (but still medium-brown) roux and may include tomatoes, while Cajun gumbos are made with a darker roux and never contain tomatoes.
Other sources claim the word gumbo comes from the Choctaw word kombo, meaning sassafrass.
The first written references to gumbo appear in the early 1800s. In 1885, the division between filé and okra-based gumbos was documented in La Cuisine Creole. The cookbook contained many gumbo recipes, some made with filé and some with okra, but none with roux..
Gumbos can be broadly divided into three categories: those thickened with okra, those thickened with filé powder, and those thickened exclusively with roux. Modern recipes of both okra and filé categories generally call for a dark roux that provides additional thickening and flavoring. Okra and filé powder are, at least historically, not used together in the same dish. You may, however, see a lighter roux combined with roped (sautéed plain to remove the 'stringy' effect) okra and topped with filé after cooking for the sweet flavor.
Filé powder, ground dried sassafras leaves, was in wide use by the native Choctaws when European colonists arrived. In modern recipes, filé gumbos use roux as their primary thickener, with the actual filé powder added as preferred at the table by the eater.
A dark roux as used in a Cajun or Creole gumbo is cooked until extremely dark. Butter will burn if used to make this type of roux, so lard or oil are the fats of choice. If the roux is to be used with okra, a lighter color may be desired, as the flavor of a dark roux is quite overpowering. Most Creole gumbos do not use as dark a roux as the Cajuns, but a medium reddish-brown type roux; the word roux is a french word that means "russet-red." The "holy trinity" of onion, celery, and bell pepper will often be cooked in the hot roux itself before the stock is added.
The traditional practice of using okra in the summer (in season) and filé in the winter has played a role in defining the kinds of gumbo usually associated with each. These associations are not hard and fast rules, but more of a general guide. For example a purely seafood gumbo is usually not thickened with filé, while one that is purely meat and game would usually not have okra. This reflects traditional practices of fishing and crabbing in warmer weather and hunting and butchering in cooler weather.
While the sausage used is traditionally andouille, other smoked pork sausages can be substituted. The sausage can be removed and replaced with fresh at the end of the cooking period, otherwise it tends to have lost much flavour to the liquid.
The ratio of soup to rice is also a point of contention. Some prefer "damp rice" and some only add a minimal amount of rice to a bowl of broth. This is strictly personal taste.
Traditional side dishes include potato salad, fresh New Orleans style french bread, crackers, or baked sweet potatoes. Many Cajuns add potato salad to their gumbo and eat it with or without rice.
In different family traditions, the dish, usually served only at the Holy Thursday or Good Friday evening meal, had to have a set number of different greens, usually seven or nine, and it would be referred to simply as, for example, "nine kinds of greens" gumbo. In the days before high-end grocery chains with their opulent produce displays, cooks were not above sneaking out to their gardens to snip off a few nasturtium or other known non-toxic leaves to make the required number.
Presumably this variation was devised in traditionally Roman Catholic New Orleans in keeping with the Lenten spirit of austerity, and may have originally consisted of greens only. But the penchant of the region's cuisine for embellishment led inevitably to the addition of local seafood (shrimp, oysters, crabmeat, and sometimes fish) — which were at least permitted under the Catholic Church's fasting guideline — and eventually seasoning meats (ham, sausage, bacon, even beef)--which were not.