5 ounces queso fresco or Muenster cheese, cut into 1/2-inch dice (1 cup)
1/3 cup sour cream
1 tablespoon chopped flat-leaf parsley
Lime wedges, for garnish
In a medium bowl, soak the ancho chiles in very hot water until softened, about 10 minutes. Drain the ancho chiles and pat them dry.
Meanwhile, heat the vegetable oil in a small skillet. Add the onion and garlic and cook over moderate heat, stirring occasionally, until the onion softens, about 10 minutes. Transfer the cooked onion and garlic to a blender. Add one-third of the ancho chiles and the tomatoes with their juices and blend for 1 minute. Strain the mixture into a medium saucepan. Add the stock, oregano, thyme and marjoram and bring to a boil, then simmer for 10 minutes. Season the soup with salt.
Divide the the broken tortilla chips, cheese and remaining ancho chiles among 4 soup bowls. Ladle the soup on top. Garnish the tortilla soup with a generous dollop of sour cream and the chopped parsley and serve immediately with lime wedges.