A pupusa (from Pipil pupusawa) is a thick, hand-made corn biscuit-like flat bread (made using masa de maíz, a maize flour dough used in Latin American cuisine) that is stuffed with one or more of the following: cheese (queso) (usually a soft Salvadoran cheese called Quesillo), fried pork meat ground to a paste consistency (Salvadorian chicharrón, not to be confused with fried pork rind which is also known as chicharrón in some other countries), squash (ayote), refried beans (frijoles refritos), or queso con loroco (loroco is a vine flower bud from Central America). There is also the pupusa revuelta with mixed ingredients, such as queso (cheese), frijoles (beans), , and chicharrón or bacon. Pupusas are similar to tortillas and especially to arepas. In fact, in El Salvador, normal tortillas are about the same diameter and thickness as pupusas, without the filling.
Pupusas also known as Pupisio were first created by the Pipil tribes which dwelled in the territory which is now known as El Salvador. Cooking implements for their preparation have been found in Joya de Cerén, “El Salvador’s Pompeii”, site of a native village that was buried by ashes from a volcano explosion, and where foodstuffs were preserved as they were being cooked almost two thousand years ago. The instruments for their preparation have also been found in other archaeological sites in El Salvador.
In the late 1950s, pupusas were still not widespread across El Salvador, and were mostly localized in the central towns, such as Quezaltepeque, and cities of the country. As the population started to migrate to other areas, pupusas stands started to proliferate in the 1960s across the country and in the neighboring areas of Honduras and Guatemala, sometimes with variations in shape, size or filling. In Guatemala during the 1970s, pupusas had a half-moon shape. The half mooned shape would be considered a half eaten pupusa in the Chalatenango area, fish pupusas were uncommon, and pupusas served east of the Lempa river usually had a much larger diameter.
In the 1980s, the Salvadorian civil war forced a Salvadorian migration to other countries, mainly the United States. Therefore, pupusas became available outside the country wherever a Salvadorian community was found. In the United States, immigrants have brought the dish to Florida, New York, California, Iowa, Chicago, Nevada, North Carolina (especially Durham, North Carolina), Maryland, Virginia, Washington, D.C., Texas, East Boston, New Jersey, Nebraska, Lancaster, PA, St. Paul, Minnesota, Northwest Arkansas, Columbus, OH, Atlanta, Portland,OR, Nashville, TN and other locations, where there are now many pupuserías (a place where pupusas are sold and made). In Canada, pupuserías may be found in Toronto, (North York and City of York), Kensington Market, Southern Ontario, Eastern Ontario, Montréal, Québec, Winnipeg, Manitoba, Alberta and in Vancouver, BC.
Both at home and abroad, pupusas are traditionally served with curtido (a pickled cabbage relish, similar to German sauerkraut and Korean kimchi that comes in mild and spicy varieties) and tomato sauce, which are traditionally eaten by hand.-(Wikepedia)