When used in an idiom, the "whole enchilada" means the whole thing.
Enchiladas originated in Mexico, where the practice of rolling tortillas around other food dates back at least to Maya times. The people living in the lake region of the Valley of Mexico traditionally ate corn tortillas folded or rolled around small fish. Writing at the time of the Spanish conquistadors, Bernal Díaz del Castillo documented a feast enjoyed by Europeans hosted by Hernán Cortés in Coyoacán, which included foods served in corn tortillas. (Note that the native Nahuatl name for the flat corn bread used was tlaxcalli; the Spanish give it the name tortilla.) The Nahuatl word for enchilada is chīllapītzalli/t͡ʃiːlːapiːˈt͡salːi/ which is formed of the Nahuatl word for "chili", chīlli/ˈt͡ʃiːlːi/ and the Nahuatl word for "flute", tlapītzalli/t͡ɬapiːˈt͡salːi/. In the 19th century, as Mexican cuisine was being memorialized, enchiladas were mentioned in the first Mexican cookbook, El cocinero mexicano ("The Mexican Chef"), published in 1831, and in Mariano Galvan Rivera's Diccionario de Cocina, published in 1845. An early mention, in English, is a 1914 recipe found in California Mexican-Spanish Cookbook, by Bertha Haffner Ginger.
In their original form as Mexican street food, enchiladas were simply corn tortillas dipped in chili sauce and eaten without fillings. There are now many varieties, which are distinguished primarily by their sauces, fillings and, in one instance, by their form. Various adjectives may be used to describe the recipe content or origin, e.g. enchilada tapatia would be a recipe from Jalisco.
Enchiladas con chile rojo (with red chile) is a traditional red enchilada sauce, composed of dried red chili peppers soaked and ground into a sauce with other seasonings, Chile Colorado sauce adds a tomato base.
Enchiladas con mole, instead of chili sauce, are served with mole, and are also known as enmoladas.
Enchiladas placera are Michoacán plaza-style, made with vegetables and poultry.
Enchiladas poblanas are soft corn tortillas filled with chicken and poblano peppers, topped with oaxaca cheese.
Enchiladas potosinas originate from San Luis Potosi, Mexico and are made with cheese-filled, chili-spiced masa.
Enchiladas suizas (Swiss-style) are topped with a white, milk or cream-based sauce, such as béchamel. This appellation is derived from Swiss immigrants to Mexico who established dairies to produce cream and cheese.
Gravy-style enchiladas are the dominant variety found throughout South and Central Texas. These have a gravy-like chili sauce over either cheese-filled or beef-filled corn tortillas, and are topped with a layer of cheese.
Enchiladas montadas, stacked enchiladas, are a New Mexico variation in which corn tortillas are fried flat until softened but not tough, then stacked with red or green sauce, chopped onion and shredded cheese between the layers and on top of the stack. Ground beef or chicken can be added to the filling, but meat is not traditional. The stack is often topped (montada) with a fried egg. Shredded lettuce and sliced black olives may be added as a garnish.
Enchiladas Duranguenos are made with red chile sauce stuffed with queso cotija and minced onions. Some people use Parmesan cheese instead of queso cotija because it is cheaper.
In Costa Rica, the enchilada is a common, small, spicy pastry made with puff pastry and filled with diced potatoes spiced with a common variation of tabasco sauce or other similar sauces. It is typically eaten in the afternoons in the coffee break, and available in almost every bakery in the country. Other variations include fillings made of spicy chicken or minced meat.
In Honduras, enchiladas look and taste very different from those in Mexico; they are not corn tortillas rolled around a filling, but instead are flat, fried, corn tortillas topped with ground beef, salad toppings (usually consisting of cabbage and tomato slices), a tomato sauce (often ketchup blended with butter and other spices such as cumin), and crumbled or shredded cheese. They look and taste much like what many people call a tostada.
In Nicaragua, enchiladas are different from the other ones in Central America and resemble those in Mexico; they are corn tortillas filled with a mixture of ground beef and rice with chilli, they are then folded and covered in egg batter and deep fried. It is commonly served with a cabbage and tomato salad (either pickled salad or in cream and tomato sauce). The Nicaraguan enchilada resembles the Empanada of other countries.
In Guatemala, enchiladas look much like Honduran enchiladas but the recipe is different. Usually starts with a leaf of fresh lettuce, next a layer of picado de carne, which includes a meat (ground beef, shredded chicken, or pork) and diced vegetables (carrot, potato, onion, celery, green bean, peas, red bell pepper, garlic, bay leaf, a you can season with a little salt and black pepper) next is the curtido layer which includes more vegetables (cabbage, beets, onions, and carrots) next is about two or three pieces of sliced hard boiled egg, next layer is thin sliced white onion, next layer is a drizzle of red (not spicy) salsa, next topped with either queso seco or queso fresco and lastly topped with cilantro.
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Mariano Galvan Rivera, Diccionario de Cocina o el Nuevo Cocinero Mexicano en Forma Diccionario, Second edition (Mexico: Imprenta de I Cuplido, 1845).
El Cocinero Mexicano o coleccion de los mejores recetas para guisar al estilo americano y de las mas selectas segun el metodo de los cocinas Espanola, Italiana, Francesca e Inglesa, 3 vols. (Mexico City: Imprenta de Galvan a cargo de Mariano Arevalo, 1831), 1:78-88.
Look up enchilada in Wiktionary, the free dictionary.