New Mexico Green Chile Sauce

In New Mexicoa question you will commonly here is "Red or Green?"
This would be Green.

2 tablespoon unsalted butter or lard
1 cup chopped onion
2 tablespoons flour
1 1/2 cups chicken broth
1 cup (or more) chopped roasted green chiles (fresh or frozen please)
2 large cloves of garlic, finely minced
Salt (optional)
1/2 teaspoon ground cumin

Melt butter in a saucepan over medium heat.
Add the onion and saute until soft. Stir in flour and the broth until mixture is smooth.
Add chiles, garlic, cumin and simmer for 10 to 15 minutes, adding salt to taste.