Season the beef with salt and pepper, then sear in 4 tablespoons of oil in a hot cast iron skillet for 5 minutes on each side.

Put it into a crockpot with 8 cups of water and cook on high until tender. This will take 4 to 5 hours.

Preheat a couple of tablespoons of oil in a deep skillet or Dutch oven and add the onions, garlic, and some salt and pepper. Saute for 6 to 8 minutes.

Next, put 2 cups of the chiles in a blender and add a cup of the liquid from the crockpot.

Blend until smooth.

Cut the rest of the chiles into thin strips.

Put the shredded beef, pureed sauce and 3½ cups of the remaining broth into the pot with the garlic and onions, and bring to a boil.

Turn the heat down and simmer for 20 minutes.

Add the potatoes to the pot (or fry them in oil to crisp them up and add flavor).

Add the sliced chiles and then simmer for half an hour until the potatoes are cooked and the sauce has reduced a bit. If you prefer more liquid, you can stop cooking when the potatoes are only just tender.