Place tomatillos, onion and chiles on a baking sheet and drizzle with olive oil.
Place in a 500 degree F oven for 20-30 minutes or until skins blackened. Watch it closely. Rotate a few times until peppers and tomatillos are softened and blackened. Allow to cool and peel skins from peppers.
Place all roasted vegetables into a blender with 1 1/2 C cilantro, garlic and as much chicken broth as you need to get your desired consistency. (1/2 cup to 1 cup)
Season with salt and add sugar if needed.
Enchiladas
Soften tortillas by cooking them in a dry skillet for 5 seconds on each side. Cover with a paper towel.
Dip tortilla into sauce on both sides. Place in bottom of baking dish.
Place chicken and cheese into middle of tortilla and roll up. Place seam side down in a 9 x 13 pan.
Repeat with remaining tortillas.
Spoon additional salsa over top and sprinkle with cheese.
Bake at 375 degrees F for about 20 minutes.
After baking garnish with some additional sauce, sour cream and a sprinkle of remaining cilantro.
Notes
Roasting peppers deepens the flavor. It caramelizes the sugars in the peppers and makes them a little sweater and also gives the pepper a touch of smokiness.