Roast the chiles. I do it on the grill. When they're cool, remove the skins and seeds. I prefer pablano chiles, but use whatever is handy.
Dice the onions, chop the garlic, dice the potato, chop up the chiles. Also dice the pork. I might use a small pork roast or a few chops' worth of meat. It depends on how meaty you want the green chile to be. You can even leave it out to make it vegetarian (substitute vegetable broth for chicken).
Sweat the onions and garlic in the olive oil over medium heat. Add salt & pepper to taste. When onions become translucent, add flour to make a roux. Cook roux for a few minutes, then add broth, stirring to break up lumps. Bring to a boil, then reduce heat to simmer. Add potato and pork. Simmer for an hour.
Remove from heat, chop cilantro and add it to the chili. Stir and serve.