Heat a 10-inch cast-iron skillet to medium-high heat. Place whole green chilis in the pan.
Char until extra black on several sides. This takes about 10 minutes. Remove from pan and allow to cool.
Roast Tomatillos
Heat a smaller cast iron skillet if you have it. Char tomatillos on several sides, just like chilis. Remove from pan and allow to cool enough to handle.
Puree Tomatillos
Quarter roasted tomatillos and puree in a food processor or blender on low speed.
Combine and Cook Salsa
Remove stems from roasted chilis. Place whole chilis in a food processor with pureed tomatillos. Pulse a few times on low speed to mix chilis with tomatillos. Don't over-blend.
Pour salsa into a saucepan and bring to a boil with the lid on. Reduce heat and simmer for 5 minutes. Add salt to taste. Allow to cool to room temperature.
Store
Finished salsa will last easily a week refrigerated or 3 months frozen.
Notes
Preparation Tips:Roast chili peppers in a single layer. Use a spatula to flatten cooking peppers. It will help shape them with square sides, and that makes them easier to brown on several surfaces.Tuck tomatillos tightly into a smaller cast iron skillet. Then, you can turn and arrange them without having them roll around in the pan.Be sure to puree tomatillos briefly by themselves and pulse-chop mixture once you add roasted chilis. Don't over-blend.