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French Onion Soup

You'll have the most success if you use an enameled cast iron pan. When I've used a good stainless steel pan, the kind with a thick aluminum/steel sandwiched bottom, I've found it impossible to get the onions brown enough without burning. The onions will go from beautiful to black in half-a-second, always just right before you think they will.

Cooking the onions 20 minutes at a time allows parts to stick to the bottom and get even more brown. Allowing that to happen, then scraping and stirring that into the soup, will give you much deeper flavor than stirring so often that nothing sticks to the bottom.

I would not make this without the sherry (or port, or even Marsala, or maybe just a red wine) and the balsamic vinegar. There are no distinct flavors in this soup (you'd never know there was balsamic vinegar in it), but they're all necessary to contribute to the overall flavor.
Prep Time 45 minutes
Cook Time 2 hours
Total Time 2 hours 45 minutes

Ingredients

Broth

  • 6 oz butter
  • 1 tsp salt
  • 8 large onions sliced thin (I use a combination of sweet, yellow, and white)
  • 2 oz sherry
  • 2 oz balsamic vinegar
  • 1 qt chicken stock
  • 1 qt beef broth
  • bouquet garni or similar herbs (like a few springs of thyme, some sage, etc.)

Croutons

  • sturdy French or Italian baguette sliced 1/2"–1" thick
  • olive oil
  • salt
  • 12 oz Gruyere cheese shredded (or cheat and use Swiss)

Instructions

Soup

  1. Place the butter and salt in a large pot, preferably an enameled cast iron pot.
  2. Heat the butter over medium heat until it begins to brown.
  3. Add the onions and cook over medium heat for about 20 minutes. If you're using a thin pan (even one with a thick, stainless/aluminum sandwiched base), you'll have to stir frequently. If you're using an enameled cast iron pan, you don't have to worry about burning so much.
  4. Stir the onions, scraping the bottom of the pan until all of the stuck bits are free.
  5. You want the onions a deep, dark, caramel brown color. Cook for another 20 minutes, scrape, cook again . . . It usually takes me about an hour and a half to cook out most of the liquid generated by the onions and to get the onions dark enough.
  6. When the onions look like melting caramel, increase heat to medium high.
  7. Stir in sherry and vinegar.
  8. Cook for a few minutes.
  9. Scrape and stir.
  10. Add chicken and beef stock.
  11. Add herbs.
  12. Bring to a boil for a minute or so.
  13. Reduce heat to simmer.
  14. Season with salt and pepper to taste.
  15. Simmer for about an hour, skimming off any foam that forms on the top.

Croutons

  1. While the soup is simmering, place the baguette slices on a cookie sheet.
  2. Sprinkle with olive oil and a little salt.
  3. Bake in 350° oven for about 20 minutes, or until toasted.

Assemble the soup

  1. Ladle soup into individual oven-safe bowls that you've place on a cookie sheet.
  2. Place as many croutons as will fit on top of the soup.
  3. Cover croutons with shredded cheese. Don't be afraid to have it slop onto the bowl, and don't be stingy.
  4. Place the cookie sheet full of soup bowls under a broiler until the cheese bubbles and begins to brown.