Heat the oil in a skillet or saucepan over medium heat. Add the onions, and saute for 5 minutes. If using jalapeno, add now.
1 cup Onion, 2 Tablespoons Olive oil, 1 Jalapeno
Add the garlic, and saute one more minute.
2 Tablespoons Garlic
Add the remaining ingredients and bring to a simmer for 10 minutes, until the sauce reduces by about 20% and is chunky and thickened.
1 cup Green chiles, 1 teaspoon Oregano, 2 cups Chicken broth, 1 teaspoon Cumin, 1 teaspoon Cayenne pepper
Add the sauce to a food processor and blend for about 60 seconds, or until the color lightens and the sauce is totally smooth. Season with salt and pepper to taste.
½ teaspoon Pepper, ½ teaspoon Salt
Serve and enjoy!
Notes
You can adjust the thickness of the sauce by simmering it for longer or reducing the amount of broth added. If you're using tomatillos, I recommend adding half or less of the broth, as the tomatillos will add a lot of liquid.
You can easily make this green enchilada sauce vegan by swapping the broth out for vegetable broth.
For a fresher, brighter sauce, swap out the canned chiles for any sort of roasted green chile pepper. Poblano peppers, seranno peppers, and jalapenos will all work great- just give them a roast, or saute them with the onions.
If you're adding cilantro, it's best to use this sauce as a finishing sauce- that is, don't use it in recipes you need to bake again. This will mute the cilantro flavor considerably.