In a large saucepan, heat grease or oil over medium heat and saute onions until tender and starting to brown at the edges, about 10 minutes. Add garlic and continue to cook until fragrant, about 2 minutes.
Transfer onion and garlic to a blender with tomatillos, 1/2 cup of green chiles, oregano, salt, and pepper. Pulse until chopped fine, but not pureed. In the same saucepan, toast the cumin and coriander over medium heat, stirring, for 1 minute until fragrant.
Pour the blended sauce mixture back into the saucepan and stir in chicken broth, liquid smoke, and remaining 1/4 cup of diced green chiles; simmer for 30 minutes. Taste the sauce and add sugar, one teaspoon at a time, to desired taste.
Yields 2 1/2 cups of sauce. Enough for two 9 by 11-inch pans of enchiladas, or roughly 20 servings.
Store in a glass jar with a lid for up to 1 month in the refrigerator or freeze for up to 3 months.