Turn on the broiler and place a rack 5 inches away from heating element. Line a cast-iron skillet or baking sheet with foil and place the Hatch chiles on the skillet. Cook under the broiler for 7 minutes, and then remove the skillet from the oven. Turn over the Hatch chiles and continue to broil the chiles for 7 to 8 more minutes or until nicely charred.
After this time, remove the skillet from the oven. Place the chiles in a paper sack or plastic food-storage bag, close it tight and let the chiles steam for 20 minutes. After the chiles have steamed, remove from the bag and rub off the skin. Remove the stems and seeds from the chiles then dice.
Add the diced potatoes, chiles, garlic, cumin, salt, black pepper, and cayenne pepper to the skillet and mix well with the onions and garlic.
Hatch chile potato casserole | www.homesicktexan.com