In a pan over medium heat add 1 tablespoon of oil with tomatillos, onion, and peppers. Roast until charred, turning over as one side is done roasting.
Add garlic and roast for a minute or two.
Note: It is not necessary to roast all except tomatillos but sometimes when I make this sauce I will roast all together. Also remember to rinse tomatillos well as when you remove husk the tomatillo skin is sticky.