How to Make It
In a large saucepan, heat the oil. Add the chopped tortillas and garlic and cook over moderately high heat, stirring occasionally, until the tortillas are crisp and the garlic is browned, about 3 minutes.
Add the minced onion to the saucepan along with the tomato puree and bring to a boil. Add the stock, chili powder, bay leaf and cumin and bring to a boil. Simmer over low heat until reduced to 1 quart, about 30 minutes. Discard the bay leaf.
Working in batches, puree the mixture in a blender. Add a pinch of cayenne and season with salt.