Pachamanca (from Quechua pacha "earth", manka "pot") is a traditional Peruvian dish based on the baking, with the aid of hot stones (the earthen oven is known as a huatia), of lamb, mutton, alpaca, pork, chicken or guinea pig, marinated in spices. Other Andean produce, such as potato, green lima beans or "habas", sweet potato, occasionally cassava or yuca, and humitas (sweet treat) as well as ears of corn, tamale and chili, is included in the baking.
The dish is essentially made in the central Peruvian Andes in three main regions: 1) The upper Huallaga valley, in Huánuco and Pasco vicinity, where it is made with pork and seasoned with chincho, a local herb; 2) in the Mantaro valley and neighboring area around cities like Huancayo, Tarma and Jauja; they use lamb and a different seasoning; and 3) in several places of Ayacucho department. In the Peruvian Amazonia, the southern and northern Andes, and the mostly desertic coast the dish is uncommon due to the lack of firewood or the type of stones needed without any content of sulphur. Meat is wrapped in marmaquilla or chincho leaves before being put in this kind of earthen stove.
This important part of Peruvian cuisine, which has existed since the time of the Inca Empire, has evolved over time, and its consumption is now widespread throughout modern Peru, where regional variations have appeared in the technical process of production, but not in the ingredients or their baking. It's important to note that the preparation is not only limited to Peru, but also that it exists with minimal variants in other Andean countries, for example Ecuador.
Preparation begins with the heating of stones over a fire, and the meat is then placed on top. The fire is covered with grass and earth, and the resulting oven is opened up after around two hours. Usually, a large quantity of meat is cooked, perhaps a whole sheep, to serve several people.
An ancient process devised by the Peruvians is the preservation of potatoes by "freeze-drying" them for future use. First, the potatoes were spread-out under the sun during the dry months of June and July, which are also the coldest months in Peru. For a period of 3 to 4 days, the potatoes were exposed to hot temperatures during the day, and below 0° degree temperatures at night, until one was left with chuño - a natural crisp potato. This exposure to the heat and the cold made them naturally "freeze- dried." During the drying process, at the end of each day the potatoes were crushed to extract their liquid, and frozen all over again at night. This process was repeated several times until the potatoes were completely dehydrated. After drying, the dry potatoes would be trodden under foot to loosen their skins, and the skins were eventually peeled-off by hand. After peeling, the potatoes were placed inside a reed-like basket, and the basket inserted into running river water, whose waters were very cold, and left there for about 3 weeks. Afterwards, the moraya was collected, dried, and then pounded into a flour. The flour could last up to 4 years, without spoiling. The Peruvians made a soup from the moraya flour, mixed with garlic, fresh potatoes, carrots and onions. The huatia oven, or an earthenware oven, were traditionally used for cooking the moraya soup.