In a 6 quart pan, heat the oil and saute the onion until softened. Add the garlic and cook for 1 minute more. Stir in flour, chili powder and cumin. Cook for a minute or two. Gradually whisk in the milk. Add the rest of the ingredients, except the cilantro if using fresh. Stir and bring to a boil. Reduce heat and simmer for 15 minutes. Stir in the cilantro. Can garnish with more cilantro if desired.