On a half sheet pan, arrange the tomatillos, peppers, onions, and garlic and drizzle with the oil.
Place the sheet pan directly on the grill grates and roast on the grill 30-40 minutes until the peppers skin has blistered and tomatillos are roasted.
Reserve 1/2 the roasted onion, peel the garlic cloves, peppers, and remove the seeds and stems from the peppers.
In a blender or food processor, place the remaining half onion, peeled garlic, roasted peppers, lime juice, salt and pepper and blend on low until mostly smooth.
Add the cilantro and chicken stock and blend until desired consistency.
Taste and adjust seasoning as desired.
Use for enchiladas, and top the enchiladas with the remaining roasted onions.
Notes
Recipe makes 3 1/2-4 cups of sauce, enough for a large batch of enchiladas!