To start off you are going to need some fresh green chilies. They are commonly labeled Anaheim (if you are lucky you will find fresh Hatch or Pueblo chili peppers) in many grocery stores in America. Most in commercial grocery stores are mild, and I would choose mild for this recipe, although certain years the chilies are hotter than other years, a factor that depends on the weather and drought conditions. If you can't find fresh green chilies, you can use canned green chilies which are commonly found on any Mexican food isle, there are several manufacturers of canned green chilies, I would definitely choose the Hatch brand if fresh can't be found. Frozen may also be an option, but I have only seen frozen in local grocery stores in Colorado and New Mexico.

If you are lucky enough to spot a guy with a chili roaster that is definitely your cue to stop and buy some rotisserie roasted chilies right off the farm, they will sell them to you in bags that can be used right away or frozen. If you can't find that guy and have a grill you can roast the chilies on your barbecue grill. You'll need a pair of tongs and you'll have to stay with them until the skins are darkened to brown and even partially blackened. After roasting put them in a brown paper bag and that paper bag into a plastic zip lock bag. Double bagging is necessary since the bottom of some paper bags will fall out. If you don't have a barbecue grill or simply want to work indoors, the chills can be broiled in the oven on HI. Spread your chilies and tomatillos onto a baking sheet. Broil them,  rotating every so often until the skins are darkened on all sides, to a deep golden to dark brownish black. Again, you will have to stay with them and watch them or they will burn. Place the roasted peppers into a paper bag and that paper bag onto a plastic zip lock bag. Once the peppers have softened and cooled their skins are easy to remove.  After they have cooled completely, scrape the skins from the chilies, cut the tops off and then cut them in half so you can remove the seeds, especially if they are hot, but I never remove all the seeds, I always leave a least a few.  If you choose to add a Serrano or two, it's a good idea to remove the seeds.  Then dice the chilies into a fairly fine dice. Take the cooled tomatillos and peel them.

Next...

Heat a deep pot to medium heat with 2 tablespoons of butter and olive oil, add the diced onions, saute until golden brown, to that add the cubed pork then sear and brown, by stirring the pork cubes by stirring often. After the pork is browned, add the minced garlic and cumin, stir and coat well for about two minutes. To this add the broth, the chilies, Serrano chilies, the tomatillos, and last but not least the roasted diced green chilies. Heat everything to a slow boil, then reduce the heat a bit, and let this all simmer for about an hour.  After it's been simmering it will thicken some.   Slowly add the flour/water mixture one tablespoon at a time until the pot just thickens (you may not use all 6 tablespoons), of course thickening can be a personal matter but the green chili should be medium thick, like thick tomato soup or stew.  Serve your delicacy hot, put the leftovers into smaller containers and refrigerate or freeze,  next day green chili is even better because the flavors have melded.

Burritos in Colorado come smothered or not, so do chili rellenos, if one orders their burrito smothered, it will come covered in green chili.  I like my green chili many ways but in a bowl on a chilly day is my favorite, topped with onions and/or cheese or both.