Peel the outer husk/skin off the tomatillos, onion and garlic. Slice onion in half. Place on a baking sheet along with the chiles (remove seeds from chiles if you want less heat).
Place under the broiler or on the grill of your BBQ and roast the tomatillos, onion, chiles and garlic until charred all over.
Let chiles cool and scrape burnt, charred skin off (optional). Place the tomatillos, peppers, onion, garlic, vinegar (or lime juice) and salt in a food processor, blender or Vitamix, and pulse until smooth. Season to taste with salt.
Notes
Thin the roasted salsa verde with chicken stock until it's the right consistency for pouring over enchiladas before baking. Works and tastes amazing!