This recipe is one of several included in the Texas Monthly article From Husks Till Dawn by Patricia Sharpe, [March 2007]

2 pounds tomatillos (about 14 medium), husked
1 large onion, coarsely chopped
2 to 4 garlic cloves (as desired)
2 to 3 serrano chiles (or 2 to 4 jalapeños)
1/2 cup coarsely chopped fresh cilantro (about 1/2 bunch)
1 avocado
1 tablespoon olive oil
juice of 1 large lime or 2 to 3 Mexican limes (about 2 tablespoons)
1 teaspoon kosher or sea salt, or more to taste

Bring a medium saucepan of water to a boil. Add tomatillos and simmer until they turn drab green and soften, 8 to 10 minutes. Drain and transfer to a food processor or blender. Cool briefly, then add remaining ingredients. Pulse to break down the tomatillos, then purée until smooth. Taste for seasoning and add more salt or lime juice as desired. May be refrigerated up to 5 days. Makes about 4 1/2 cups.