An underground pressure cooker
The traditional curanto of Chiloé is a display of thermal engineering that predates modern cookware by millennia. The process begins by digging a pit, typically about a half-meter deep, and lining it with smooth, non-porous river stones. A fire is built on top of these stones and burns for several hours until they are glowing red-hot. Once the stones reach the required temperature, the embers are swept away, and the cooking process begins with remarkable speed to conserve the stored thermal energy.
The first layer placed directly on the hot stones often consists of shellfish, such as mussels (choros) and clams (almejas). The heat from the stones instantly vaporizes the liquid from the shellfish, creating a massive amount of steam. Subsequent layers of pork, chicken, sausages, potatoes, and potato-based breads called milcao and chapalele are added on top. Each layer of food is separated by massive leaves from the nalca plant (Gunnera tinctoria), a species called Chilean rhubarb. These waterproof leaves can grow up to 2.5 meters in diameter and act as a gasket, trapping the steam inside the pit. Finally, the entire pit is covered with wet sacks and a thick layer of turf and soil, creating a sealed, subterranean pressure cooker.
Thermodynamics of an ancient kitchen
The curanto oven cooks food through a combination of conduction, convection, and steaming. Conduction occurs where the food directly touches the hot stones or other ingredients. The trapped, superheated steam circulates through the layers of food in a process of convection, ensuring everything cooks evenly without burning. Water has a thermal conductivity 24 times greater than air, which makes this steam-based method efficient. The entire feast can be cooked in about one to two hours.
Archaeological evidence from the Chiloé Archipelago, such as a 6,000-year-old cooking pit found at the Puente Quilo site, confirms the antiquity of this technique. This method of cooking was developed long before the introduction of pottery to the region, providing a way to steam and boil food for large groups. The name "curanto" itself derives from the Mapudungun language word kurantu, which means "stony ground." This practice is believed to have originated with the Chono people, who were hunter-gatherers in the region thousands of years before the arrival of the agriculturalist Mapuche-Huilliche.