In a classic fairy tale, a lone traveler teaches a village about sharing by getting everyone to contribute an ingredient to his stone soup until the humble dish becomes a delicious dinner for the whole community. While the story is simply a fable, a real version of stone soup exists in Oaxaca, a southwestern state of Mexico, and its origins are also communal.

A specialty of the Chinantec people who live along the Papaloapan River, caldo de piedra (literally “stone soup”) is a fish-based soup made right on the banks of the river where the animals are caught. Fishermen portion the soup’s ingredients—fish or freshwater shrimp, plus water, tomatoes, onions, lime, and cilantro—into bowls made of hollowed dried gourds (jicaras). Meanwhile, a cook builds a fire and heats small river rocks for about two hours, until they’re scorching hot. Using long tongs, he then transfers a stone into each bowl. The intense heat of the rock roils the liquid and cooks the soup in a matter of minutes.

Caldo de piedra is a communal dish; after all, it’s a group effort to catch the fish, prepare the individual servings, and build the fire. Early versions of the soup were whole-village affairs. The ancient Chinantecs carved river boulders into large cauldrons. Inside the stone pots, they would cook great quantities of caldo de piedra to be shared among the village, not entirely unlike the stone soup in the fable.