1Begin by preparing the chiles for the sauce. Remove the stems and seeds from the Guajillo chiles and Ancho chile. Heat a dry comal or skillet over medium heat and toast the Guajillo chiles and Ancho chile for 30 seconds per side until fragrant, being careful not to burn them. Place the toasted chiles in a bowl and cover with hot water; let them rehydrate for 20 minutes.
2While the chiles rehydrate, prepare the sauce base. In a small saucepan, boil the Roma tomatoes until softened, about 10 minutes. Drain and set aside. In a separate pan, heat 10 grams of Lard over medium heat. Sauté the White onion and Garlic cloves until softened and fragrant, about 5 minutes.
3Once the chiles are rehydrated, drain them, reserving a small amount of the soaking liquid. In a blender, combine the rehydrated Guajillo chiles, Ancho chile, boiled Roma tomatoes, sautéed White onion, sautéed Garlic cloves, Corn tortilla, Chicken broth, and 2 grams of Salt. Blend until very smooth, adding a little reserved chile soaking liquid if needed to achieve a pourable consistency.