Peel the outer skins off the onion and garlic and discard.
Line a baking sheet with parchment paper or foil and add the green chiles, garlic, jalapeño and onion. Place under the broiler until charred all over, turning over half way through, about 10 minutes.
Remove from broiler, cover with foil and allow to rest and steam for 5 minutes. Peel and rub the charred skins off of the green chiles as best you can. (See Note 4)
Place all the roasted green chiles, garlic, jalapeño, onion, cilantro, cumin, oregano, kosher salt and chicken stock in a food processor, blender or Vitamix, and pulse until smooth. If you prefer it a little smoother, then add more chicken stock to suit your needs.
Pour the mixture into a saucepan with the oil and simmer on low for 15 minutes. Remove from heat and allow to cool. Season to taste with salt. Optional: add a teaspoon of white vinegar or lime juice to adjust taste to your liking.
Video
Notes
Hatch Chiles as well as Poblanos can be substituted for the Anaheim chiles. I prefer a combo.
If you'd like this spicier, substitute a Serrano chile or if milder, omit the jalapeño all together.
Mexican oregano is a relative of Lemon Verbena and is native to Mexico. Similar in that it’s pungent like Mediterranean oregano, Mexican oregano has notes of mild licorice and citrus. Mediterranean oregano is a member of the mint family and most often is used in Greek and Italian recipes. Mediterranean oregano is the one most found in spice racks and supermarkets.
If you prefer the sauce to be milder, make a vertical slice into each chile and remove the seeds and membrane.
Optional: add a teaspoon of white vinegar or lime juice to adjust taste to your liking.