Discard husks and stems from tomatillos; wash thoroughly. Place tomatillos on an aluminum foil-lined baking sheet. Broil tomatillos 3 inches from heat 6 to 8 minutes or until tomatillos look blistered, turning once. Let cool.
Process garlic in food processor until garlic is minced. Add jalapeño pepper to garlic; process until minced, stopping once to scrape down sides.
Cut avocado in half, and remove seed; cut avocado into quarters, and peel. Add tomatillos, avocado, and remaining 3 ingredients to jalapeño pepper mixture. Process 15 seconds or until tomatillos are pureed. Cover and chill 1 hour.