In the famed onion soup au gratin at Les Halles in Paris, grated Gruyère is used in place of Parmesan. They are interchangeable in this recipe.
AMERICAN CHEESE SOUPS
In this era of fine canned soups a quick cheese soup is made by heating cream of tomato soup, ready made, and adding finely grated Swiss or Parmesan to taste. French bread toasted and topped with more cheese and broiled golden makes the best base to pour this over, as is done with the French onion soup above.
The same cheese toasts are the basis of a simple milk-cheese soup, with heated milk poured over and a seasoning of salt, pepper, chopped chives, or a dash of nutmeg.
Chicken Cheese Soup
Heat together 1 cup milk, 1 cup water in which 2 chicken bouillon cubes have been dissolved, and 1 can of condensed cream of chicken soup. Stir in ¼ cup grated American Cheddar cheese and season with salt, pepper, and plenty of paprika until cheese melts.
Other popular American recipes simply add grated cheese to lima bean or split bean soup, peanut butter soup, or plain cheese soup with rice.
Imported French marmites are de rigueur for a real onion soup au gratin, and an imported Parmesan grinder might be used for freshly ground cheese. In preparing, it is well to remember that they are basically only melted cheese, melted from the top down.
CHEESE SALADS