1Heat broiler. Place tomatillos, the peppers and garlic cloves in foiled-lined broiler pan. Broil 3 to 4 inches from heat, turning occasionally, until tomatillos are roasted and peppers are slightly blackened, about 10-15 minutes. Remove from broiler.
2Pour chicken stock over vegetables. Let stand 10 to 15 minutes, until cool enough to handle. Remove vegetables, scraping bottom of pan with wooden spoon, if necessary, to loosen; reserve chicken stock.
3Remove any overly blackened skin from tomatillos. Peel peppers; seed*. Squeeze garlic from skins.
4In food processor, place tomatillos, the peppers, garlic, onion, cilantro, lime juice, salt and half of the reserved chicken stock. Cover; process, using quick on-and-off motions, until blended. Add more reserved chicken stock, if necessary, for desired consistency. Serve immediately or refrigerate until ready to serve.