This is classic New Mexican Green Chile. There are just a few aromatics and no herbs and spices to muddy the flavor. Removing the skin and seeds can be a chore as they want to stick to your fingers. Dipping the chile and your fingers in water makes the task a breeze however, you want to use that water as part of the sauce because all of the tasty liquid that collects inside the chile as it roasts would be lost otherwise.
Holding the chile over a bowl to catch any juice, use your fingers to remove the skin of the roasted chile. Most of the skin should slide off easily. You may need to work on a few bits here and there. Remove as much skin as possible but a few bits of stubbornly sticking skin aren’t a problem.
Shake whatever skin you can from your fingers (it has a tendency to cling desperately to your fingers) then dip your fingers and the chile in the bowl of water to remove the clinging skin.
Still holding the chile over a bowl, remove the stem end. You can usually do this by pinching the top of the chile but a pair of kitchen shears works well, too.
Discard the stem end and any seeds that cling to it.
Split the chile in half lengthwise. Again, this is pretty easy to do with a fingernail.
Dip the chile into the bowl of water and scrape away the seeds.
Put the cleaned chile into a clean bowl and repeat the process with the remaining chile.
Cut the chile into long strips.
Cut the chile crosswise into small squares
Add any liquid that has collected in the bottom of the bowl from the chopped chile to the bowl of water.
Strain out seeds and bits of flesh from the water using a three step process. Strain the water through a large sieve.
Strain the liquid through a fine, small sieve.
Strain the liquid through several layers of cheesecloth or a paper filter.
Chop the onion.
Mince the garlic.
Combine ½ cup of chopped chile, onion, garlic, strained water, and salt in a saucepan. Bring the mixture to a boil and simmer for 20 minutes.
Using an immersion blender or a regular blender puree the chile mixture. This will help to thicken the chile sauce without using a thickening agent.
Add the remaining diced chile and two cups of water to the puree and simmer until the chile is soft to the bite, but not mushy, approximately 15-20 minutes, adjusting salt approximately 10 minutes into the simmer. If you used a regular blender in the previous step, use the water to rinse out the blender jar before adding it to the pot.
The green chile can be refrigerated or frozen. It will become softer if frozen so best to cook it for a shorter time if it is going to be frozen.