Sauté the garlic in the olive oil in a soup pot until slightly browned, about 10 minutes. Add the hoja santa or watercress and sauté for 30 seconds. Add the stock, chile (if using), salt, pepper, and bay leaves and simmer for a half an hour. Remove the bay leaves and chile. Add the celery leaves just before serving.
Place 5 cubes of bread and five of cheese in 4 individual soup bowls and ladle in the soup. Sprinkle with Parmesan cheese and serve.
