In a saucepan, warm the oil over medium heat. Add the onions, chiles, and garlic, and saut‚ over medium heat until everything is softened.
Mix in the remaining ingredients and bring the sauce to a simmer. Cover and cook for 35 to 40 minutes. Allow the sauce to cool briefly.
Strain the sauce and purée the solids in a food processor. Return the puréed mixture to the sauce, stirring thoroughly.
Refrigerate the sauce overnight to allow the flavors to mingle and mellow. Use the sauce warm or chilled. It keeps for weeks.
Variation: If you prefer a thinner sauce, water this down to your preferred consistency. It will still pack plenty of pizzazz.Yields: