Tortilla Soup with Chiles and Tomatoes

Name: Tortilla Soup with Chiles and Tomatoes
Ingredients: 4 dried pasilla chiles, wiped clean, stemmed, and seeded; 2 dried chiles de á:rbol, stemmed; 1/2 pound tomatoes, quartered; 1 large white onion, coarsely chopped; 2 large garlic cloves, chopped; 2 quarts rich and flavorful chicken stock ; or 5 cups reduced-sodium chicken broth diluted with 3 cups water; 2 tablespoons lard or vegetable oil; 1 teaspoon dried epazote or oregano, crumbled; 3 to 4 cups vegetable oil for frying; 12 (6-to 7-inch) corn tortillas, cut into 1-inch squares; 1 (6-to 8-ounces) avocado, cut into 1/2-inch pieces; 1/2 cup crumbled cotija cheese (also called queso añejo) or ricotta salata, crumbled (2 ounces); 1/4 cup crema, or sour cream diluted with 1 tablespoon water; Equipment: a deep-fat thermometer; Accompaniment: lime wedges