Throughout the Viceroyalty of Rio de la Plata, the Roman Catholic Church proselytized the vast distances and founded convents. And the nuns who lived in those convents, and their Indian servants, soon became known for intricate sweets and other confections that had roots in the sweets that predominated in Moorish-ruled Spain for eight centuries until the Moors were expelled by the Catholic monarchy of Isabella and Ferdinand in 1502. Lay sisters did most of the cooking in the convents, where class differences determined much of the protocol. Jesuit missionaries created over 43 missions in the Paraná and Uruguay River regions, as well as the Rio de la Plata area. One of the trades taught to the young Indian girls at the missions was cooking. And these young women went on to become cooks in the great urban houses and the estancias (or ranches).
Wheat bread, in spite of the need to import wheat flour from Mexico or elsewhere, remained a favorite of the Spanish population. And because of the availability of wheat flour, cooks prepared empanadas, from the Spanish word empanar or “to cover with bread,” filled with various ingredients, beef and eggs and olives being one favorite of the times. Served as little snacks before the mid-day or evening meals, empanadas originated in Spain and are thought to have their origins in the various Arab or Moorish pastries prevalent at the time. An example of the small crust-covered pies typical in Arab cooking, empanadas made their way to other areas of South America, including Paraguay. Croissant-like rolls, called media lunas, became a vital part of the Argentine diet. Eaten with a special sweetened milk spread — dulce de leche — media lunas appear everywhere in the morning in Buenos Aires.
The architecture of the grand houses, built as they were around enclosed courtyards in the Spanish and Moorish style, lent themselves to entertaining. Coupled with the food traditions of the Indians, the Spanish, and the black slaves brought into the region to assist in labor-intensive agriculture, the food that simmered in the pots and on the grills of the Viceroyalty of the Rio de la Plata evolved into something recognizable as Spanish, but not really Spanish at all. Like milanesa (the name itself is a dead give away as to its Italian origins!), Argentine cooking comes from someplace else.
Bibliography
Brooks, Shirley Lomax. Argentina Cooks! Treasured Recipes from the Nine Regions of Argentina. New York: Hippocrene Books, 2003.
Crosby, Alfred W., Jr. The Columbian Exchange: Biological and Cultural Consequences of 1492. Westport, Conn.: Greenwood Press, 1971.
Karoff, Barbara. South American Cooking: Foods from the New World. Berkeley, CA: Aris Books, 1989.
Leonard, Jonathan Norton and the editors of TIME-LIFE BOOKS. “Argentina and Chile: The Temperate South,” in Latin American Cooking. New York: Time-Life Books, 1968, p. 173-184.
Lockhart, James. Spanish Peru, 1532-1560: A Colonial Society. Madison, WI: The University of Wisconsin Press, 1968.
Super. John C. Food, Conquest, and Colonization in Sixteenth-Century Spanish America. Las Cruces, NM: University of New Mexico Press, 1988.
Vasquez-Prego, Alberto. Así Cocinan los Argentinos / How Argentina Cooks. Cuarta edición. Buenos Aires, Argentina: El Ateneo, 2000.
Wright, Ione S. and Lisa M. Nekhom. Historical Dictionary of Argentina. Metuchen, NJ: The Scarecrow Press, Inc., 1978.
© 2008 C. Bertelsen
CYNTHIA D. BERTELSEN 
Hard to stop reading long enough to leave a comment! But I did have to second your interest in Argentina, where I spent two weeks in October. One of my fascinations after the obligatory beef, lamb, pasta, empanadas, and malbec, was the native-derived stews such as locro. Corn, beans, meat, sweet potatoes, and potatoes cannot be much different from what the native Argentinians ate — yet Argentina is least Indian country in South America by far, with a few small groups of indiginous people at about the level of recognition of Native people in the eastern US (leaving out Iroquois country, the Eastern Cherokee, Maine, Florida, and the Lumbee part of North Carolina). So, like the US Thanksgiving, Argentines are perhaps eating Indian food in celebration of their colonial ancestors who displaced the Indians.
Had some great fish, too.