Check out the cookbook by Huntley Dent, the Feast of Santa Fe: Cooking of the American Southwest. I use his recipe for the basic green sauce as a guide, but I often vary it. For about six of the bags of pre-roasted green chiles (maybe 9 lbs?) you buy at HEB or CM, peeled and roughly chopped, first I'll saute two medium onions, rough chopped, in a 1/4 cup of neutral oil. Cook just until the onions are translucent. Add enough flour to make a thick roux and cook just until the raw taste of the flour is gone--you don't want much color to the roux. Add about a 1/2 head of garlic, peeled and minced, and a tablespoon each of salt, ground cumin and Mexican oregano. Cook for a few minutes and then add the chopped green chiles and as many cans of tomatoes--chopped or whole, to your taste. Sometimes I also add a couple of small cans of tomato sauce as well. The amount of tomatoes is a matter of taste. I usually add two 14 oz. cans of tomatoes. Finally, add enough chicken stock--at least a quart--to get the consistency of a medium-thick soup. Cook it down in a steady boil for about 20 minutes, stirring frequently. Taste for saltiness and adjust accordingly. I'll then partially puree the sauce with an emersion blender to get my desired consistency. I still like to see pieces of tomato and green chile in my finished sauce. If you don't have a blender, then do a finer chop to the chiles, onions and tomatoes. Generally, the cookbooks say that the finished sauce should coat the back of a spoon. I'll err on the side of a little thinner vs. thicker. The sauce will thicken when it cooks with the enchiladas or the eggs and cheese. The leftovers from each frozen quart will thicken in the fridge as well.
I'll freeze the sauce in quart containers and it lasts throughout the year.