This is based on Onion Soup Les Halles, from Anthony Bourdain. Deep, layered, and rich.
Most recipes say to cook the onions for 20 minutes. All of those recipes are lying. I’ve found that the onions aren’t brown enough until they’ve cooked for 1–2 hours. The extra cooking time, and scraping the bottom, is what makes this soup so deep and satisfying.
Slice a lot of onions, with a food processor if you have one.
Put the butter and salt in a heavy pan.
Heat the butter over medium heat until it begins to brown.
Add the onions and start cooking.
Cook, stir, scrape bottom of pan; cook, stir, scrape bottom of pan; cook, stir, scrape bottom of pan . . . Until the onions are dark and caramel-colored. They will reduce by about two-thirds.
Increase the heat, stir in sherry and balsamic vinegar, cook for a few minutes.
Add chicken and beef stock.
Add herbs. I didn’t have fresh herbs, so I put some dried herbs in a coffee filter, stapled it shut, and tossed it in the pan. No, I don’t know where those staples have been.
Bring to a boil for a minute or so.
Reduce heat to simmer, season to taste with salt and pepper, and scrape off scum that forms on top. There is no nice way to say that.
Simmer for about an hour.
While the soup is simmering, start the croutons by slicing a baguette about a 1/2″ thick.
Place baguette slices on a cookie sheet, then drizzle with olive oil and sprinkle with salt.
Bake in a 350° oven for about 20 minutes, until toasted. These have been flipped over – they won’t be this brown on top when you take them out of the oven.
When the soup is done simmering, ladle it into oven-proof bowls on a cookie sheet. Put croutons on top of soup.
Cover croutons with shredded cheese.
Place the cookie sheet/bowls under the broiler until the cheese bubbles and begins to brown, about two minutes.
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.
- 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.)
- sturdy French or Italian baguette, sliced 1/2"–1" thick
- olive oil
- 12 oz Gruyere cheese, shredded (or cheat and use Swiss)
- Place the butter and salt in a large pot, preferably an enameled cast iron pot.
- Heat the butter over medium heat until it begins to brown.
- 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.
- Stir the onions, scraping the bottom of the pan until all of the stuck bits are free.
- 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.
- When the onions look like melting caramel, increase heat to medium high.
- Stir in sherry and vinegar.
- Cook for a few minutes.
- Scrape and stir.
- Add chicken and beef stock.
- Add herbs.
- Bring to a boil for a minute or so.
- Reduce heat to simmer.
- Season with salt and pepper to taste.
- Simmer for about an hour, skimming off any foam that forms on the top.
- While the soup is simmering, place the baguette slices on a cookie sheet.
- Sprinkle with olive oil and a little salt.
- Bake in 350° oven for about 20 minutes, or until toasted.
- Ladle soup into individual oven-safe bowls that you've place on a cookie sheet.
- Place as many croutons as will fit on top of the soup.
- Cover croutons with shredded cheese. Don't be afraid to have it slop onto the bowl, and don't be stingy.
- Place the cookie sheet full of soup bowls under a broiler until the cheese bubbles and begins to brown.