Boil the fresh tomatillos and chiles in salted water to cover until tender, about 10-15 minutes, drain. If using canned, just drain.
In a blender or food processor purée chiles and tomatillos along with the cilantro, onion & garlic; If using a blender, stir well, but make sure the mixture still has some texture.
Heat the Tbsp of vegetable broth in a large skillet over medium high heat. When hot, pour in purée all at once and stir constantly for 4 to 5 minutes until sauce gets darker and thicker. Add the 2 cups of broth, return to a boil, reduce heat to medium and simmer until thick enough to coat a spoon, about 10 minutes more. Add salt to taste.
Servings: