Living in the Mid-West, and a pretty rural area at that, green chilies are not prevalent so when I see fresh poblanos I usually get a pound and a half to make chili for my husband. On occasion I see frozen green chilies from New Mexico at Walmart but I'm pretty sure they stopped stocking them. However, I enjoy the experience of roasting the peppers and preparing them and the anaheims are never as good looking. So here is what I do to make green chili, and next time I will remember to take picture throughout the process.
1 Small Yellow Onion
4 Cloves of Garlic
2 Tbsp Butter
2-4 Tbsp Olive Oil
3-4 Tbsp Flour
2 Cups Chicken Stock (or water)
1 can of Rotel Diced Tomatoes with Green Chilies (Mild)
5 Large Roasted Poblanos
I actually do mine in the toaster oven at 450 degrees for 35-40 minutes or so. I watch to see that the skins have blistered so that I can remove the outer skin of the peppers. If you've never done this before what that means is that the peppers have an almost clear shiny layer that you'll be able to peel off only after roasting. To better aid in this process you can put the peppers in a zip lock bag and seal it. I have never had to do this so I do not know how long you should leave them in the bag.
To roast simply cover your pan with foil, for easy clean up, and make slits along one side of each pepper. At this point you can remove seeds if you wish. Sometimes I do it before and sometimes I do it after but it will be much easier before and you can wash your peppers thoroughly. Once they have been properly roasted and peeled you'll cut them into 1/2 inch sections (I don't worry to much about precision here because I use an emulsion blender at the end of the entire sauce making process).
Start by chopping the yellow onion and garlic and add it to your sauce pan along with the butter and olive oil. You can alter the amounts of onion and garlic to your liking and same with the butter and olive oil I simply like the combination. Cook on medium to high heat until translucent. Its during this time I add my spices usually a pinch here and a pinch there. Do not allow all your butter and oil to cook off you will need it when you add the flour. Whisk in flour. Your mixture will become thick and you'll want to make sure you keep your chicken stock close and ready to pour so your mixture does not burn. At this juncture I always feel its better to make it too thick than too thin. Adding more flour later is a pain and the sauce can always been thinned with more chicken stock. Continue whisking and add your chicken stock. Turn your heat to medium low and allow the mixture to thicken. You can then add your Rotel and diced chilies. You want to cook it for a while to allow the flavor of the green chilies to penetrate the sauce and you'll want to continue stirring or turn the heat on low so as not to burn your sauce. Then I remove the sauce from the heat and do short pulses with my immersion blender. I am not attempting to make a smooth sauce this is simply to break up so of the garlic, onion and chilies while still leaving it chunky. Be very careful and cover the pot with a lid while you do this so you do not splatter yourself with hot sauce. I think place the sauce in a container and allow it to cool before refrigerating.
That's it! If you've ever made a gravy you know how to do this. I don't really measure and every time is just a little different. Like I said next time I'll take pictures of the entire process and make sure the make it on this page. Enjoy.