Remove the stems, seeds, and veins from the chiles. In a skillet, combine the chiles, onion, garlic, and tomatoes. Cover with water and bring to a boil over high heat. Once boiling, cover and reduce to low heat. Simmer for 20 minutes, then turn off the heat and let cool.

While the chiles are cooking, cut the tortillas into triangles. Spray an 18×13-inch baking sheet with nonstick olive oil spray. Arrange the tortilla pieces on the sheet and spray the tops as well. Bake 6 tortillas at a time at 350°F (175°C) for 20 minutes, or until golden and crispy.

While the tortillas are baking, blend the chiles, cooked vegetables, and 1 cup of water (240 ml) in a blender until as smooth as possible. Strain the sauce, then heat 1 tablespoon vegetable oil (15 ml) in a skillet. Add the sauce and fry for 10 minutes, adding 3 cups of water (720 ml) as it cooks.

Once the tortillas are crispy, heat 1 tablespoon vegetable oil (15 ml) in a skillet over medium heat for 1 minute. Add the tortillas, then pour in 1 cup of the sauce and add a sprig of epazote. Cook for 30 seconds, then serve immediately.

Garnish with diced onion, crumbled cheese, and a fried egg (huevo ranchero) if desired.