- 1 pound tomatillos, hulled and washed
- 3 garlic cloves
- 1 serrano chile
- 1 cup cucumber, peeled, seeded, and roughly chopped
- 1/4 cup roughly chopped onion
- 1/4 cup roughly chopped cilantro
- 1/2 cup homemade or low-sodium canned chicken stock, skimmed of fat
- 1 tablespoon fresh lime juice
- 1/2 teaspoon coarse salt
- 1/2 cup plain nonfat yogurt
- 1/2 cup water
- 1 small avocado, peeled, pitted, and cut into 1-inch cubes, for garnish
- Heat broiler. Place tomatillos, garlic, and serrano chile in a single layer on a rimmed baking sheet, and roast until tomatillos are soft and browned in spots, about 5 minutes. Turn all items; continue cooking until other side is soft and browned, about 5 minutes more. Remove from heat; let cool slightly.
- Transfer baking sheet to a wire rack; let cool completely. Peel garlic; place cloves in the bowl of a food processor fitted with the metal blade. Add tomatillos, serrano, and any accumulated juices along with cucumber, onion, cilantro, stock, lime juice, and salt; blend until mixture is smooth. Add yogurt and the water; process until they are just combined.
- Transfer to a large bowl or plastic storage container; cover with plastic wrap. Refrigerate at least 2 hours. To serve, ladle into bowls; garnish with avocado.
Since avocado begins to discolor rapidly when exposed to air, it should be cut at the last minute.