Next time you're looking to spruce up your favorite Mexican dish, this version by Aarón Sanchez will give a spicy kick of flavor.
Preheat the broiler.
Put the onions, tomatillos, tomatoes, and garlic on a baking sheet and drizzle with the olive oil. Broil the vegetables until they are nicely charred, about 7 minutes. Remove and set aside.
In a large, dry pan over medium-low heat, toast the guajillos, turning them over halfway through, until fragrant, about 1 minute. Transfer them to a bowl. Cover them with water and let them soak until they are soft, about 30 minutes.
Add the roasted vegetables and soaked chiles to the blender in batches. Add some chicken stock and purée until the mixture is very smooth.
Transfer each batch to a bowl as it is done. Stir the batches together.
Season with salt and pepper to taste. Use right away or store in a plastic storage container. Cover, label, date, initial, and store in the refrigerator.