1. Move an oven rack to the top position for broiling. Preheat broiler to high.
2. Remove husks and wash tomatillos.
3. Place tomatillos, peppers and unpeeled garlic cloves into an oven-safe baking dish with sides. Place into the oven, 4 inches from the preheated broiler, until the tomatillos are roasted and the peppers are slightly charred on all sides, about 10-15 minutes. Rotate tomatillos, peppers and garlic during roasting to ensure all sides are slightly charred.
4. Remove the baking dish and add chicken stock to de-glaze the pan. If tomatillos, peppers and garlic are stuck to the bottom of the dish, use a wooden spoon to scrap the baking dish.
5. Once cool to the touch, peel the garlic and discard the skins (you may have to squeeze the soft garlic out of the skin).
6. For a spicier salsa, leave in all seeds from peppers, for a medium salsa, remove half of the seeds and for a mild salsa remove all seeds from peppers.
7. Add the tomatillos, garlic and peppers to a food processor as well as the onions, cilantro, lime juice and salt.
8. Add about 1/2 of the chicken stock from the baking dish and pulse the food processor 3-4 times or until the salsa has come together. You can add more chicken stock based on your own preferences for consistency.
9. Serve salsa warm, at room temperature or cold.
Notes and Tips
For easier removal of the pepper skins: as soon as you take them out from under the broiler, place them into a resealable plastic bag and leave them alone for 10 minutes, after ten minutes the steam generated from the peppers will make it really easy to remove the skins.