Avocado-Tomatillo Taco Truck Sauce

Ms. Gutierrez writes: "This is perhaps the most popular avocado sauce used by taco truck vendors in Mexico. A little sour and very creamy, it's used to top everything from totopos (fried tortilla chips) to tacos and chilaquiles. The acidity of the tomatillos keeps the avocado fresh and vibrantly green for up to three days, if refrigerated." Adapted from "Latin American Street Food: The Best Flavors of Markets, Beaches, and Roadside Stands from Mexico to Argentina" by Sandra A. Gutierrez.

• Ready In: 15 mins
• Yields: 2 1/2 cups

Ingredients

• 4 -5  medium  tomatillos, husks removed, rinsed and chopped (about 1 cup)
• 2  serrano chilies, stems removed (seeded and deveined if less heat is desired)
• 1  cup  packed cilantro, chopped (leaves and tender stems)
• 1⁄4 cup  minced  white onion
• 1⁄4 cup water
• 1  ripe Hass avocado
•  lime juice, to taste
•  salt & freshly ground black pepper, to taste

Directions

1. In food processor or blender, put tomatillos, chiles, cilantro, onions and water; blend until smooth. Add avocado flesh; blend until smooth.
2. Transfer sauce to serving bowl; season with lime juice, salt, and pepper.