Although Mrs. Contreras doesn’t speak English on screen, her recipes are clear from her deliberate motions and detailed instructions. They are also affectionately translated by her granddaughter Silvia Salas-Sánchez, who began shooting video of her grandmother cooking when she realized, she said, that “these dishes are going to be lost if someone doesn’t record them.” (At first, like many food-obsessed grandchildren before her, she tried watching, measuring and writing down her grandmother’s recipes as she cooked, but she said it was too irritating to both of them.)

Image Maria Contreras Rico, 80, has a cooking channel on YouTube devoted to the classic home cooking of Mexico. Credit... Emily Berl for The New York Times

Both women live in Southern California, though Mrs. Contreras grew up in Michoacán and lived in Tijuana for many years, where she became an expert in northern Mexican staples like flour tortillas and refried beans, which complete her plate of carne con chile. (The dish is soupy, so the tortillas are good for dipping.)

The chili we know best is very different. A big hit of cumin is one of the signatures of Tex-Mex cooking (one that the Mexican-food expert Diana Kennedy considers an abomination) and a must for Texas chili. So is coriander seed, oddly, a spice that is hardly used in Mexican cooking.

“Coriander and cumin came to Texas from the Canary Islands,” said Robb Walsh, the food historian who was one of the first to treat Tex-Mex food as its own respectable cuisine, not as a bastardization of Mexican food. The Spanish crown offered titles and land to residents of the Canary Islands, another Spanish possession off the coast of North Africa, who would uproot their families to settle the area that would become San Antonio. The first families arrived in 1731, bringing recipes rich with spices, herbs and garlic that would become the taproot of Tex-Mex taste.