The soup is finished by cracking a raw egg directly into the hot broth at the table, letting the residual heat poach it right in the bowl.
Potatoes are simmered in a milky broth with cilantro and scallion, then a raw egg is stirred in at the last minute to poach gently in the heat. Market stalls in Mérida's highland towns serve it as a warming breakfast soup against the mountain cold.