Tortilla Soup

Preheat the oven to 425°. Brush both sides of the tortillas with the vegetable oil, cut them into 1/2-inch-wide strips and spread them in a single layer on a large baking sheet. Bake for about 5 minutes, or until golden.

In a large nonreactive saucepan, combine the stock, tomatoes, potato, ancho, onion, garlic, marjoram and 1 teaspoon of salt; bring to a boil. Reduce the heat to moderate; simmer until the vegetables are almost tender, about 15 minutes. Add the zucchini and yellow squash; cook for 1 minute longer. Add the chicken and simmer until just cooked through, about 5 minutes. Season with salt.

Ladle the soup into warmed soup plates or bowl. Float a few tortilla strips on top of each serving and garnish each with several cilantro sprigs, a lime quarter and a dollop of sour cream. Serve the remaining tortilla strips on the side. Enjoy the soup right away, before the tortillas become soggy.