How To Make French Onion Soup

Ingredients
About 2 1/2 pounds yellow, white, or red onions
1/4 cup (1/2 stick) unsalted butter
Salt
4 cups beef or chicken stock (or vegetable, if you want this to be vegetarian)
Freshly ground black pepper
Fresh artisan-style bread, cut in thick slices (optional)
Gruyere or Parmesan cheese (optional)
Tools
Knife and cutting board
Wide, deep skillet OR wide saucepan (should be at least 3 quarts)
Wooden spoon
Oven-safe bowls or mugs (optional)

Instructions

1. Gather your ingredients. You should have about 2 hours until dinner; this soup takes a while to cook.
2. Cut each onion in half lengthwise, then slice into half-moons. Slice these half-moons in half again. (See this video on knife skills and good form for cutting onions.)
3. Scrape all the cut onions into a bowl. You will have at least 6 cups of chopped onions — probably more. Don't worry too much about quantities with this recipe; if you have an extra onion to use up, throw it in!
4. Cut a stick of butter in half, and then into a couple of big pieces.
5. Place your skillet or saucepan over medium heat and add the butter. Let the butter melt.
6. After the butter melts and foams up, add the onions. Stir them to coat well with butter, and sprinkled them thoroughly with about a teaspoon of salt.
7. Turn the heat to medium low, and let the onions cook. Let them cook, stirring occasionally, for at least 45 minutes. You can let them cook even longer — an hour and a half will give you deeply caramelized onions! Just let them cook, stirring at times, as you see dark color emerge. After 45 minutes they will look pale mahogany in color, like in this photo. You can let them get even darker if you like — just don't let them burn or get black. Adjust the heat as necessary.
8. As the onions reach a dark brown color, pull out your stock. The most ideal stock to use would be homemade beef stock, but I just had storebought beef broth. You can also use chicken, veal, or vegetable broth. Then, I sprinkled 3 tablespoons of flour to make a sort of rue.
9. Pour in the broth and turn the heat up a little so the soup comes to a boil. Turn the heat down again and let it simmer for at least half an hour — longer, ideally!
10. Simmer until the soup has reduced a bit and is shiny and glazed over the onions. Season to taste with salt and pepper and serve immediately!
Additional Notes:
• This is just a base recipe for onion soup. You can add many other things. I like to add a corner of star anise or a cinnamon stick with the broth, and let those spices flavor the soup. You can also add a little garlic with the onions, or rosemary. You can add wine or brandy with the broth for increased depth of flavor too. But just plain onions, salt, pepper, and broth will still give you a sublime soup, if you cook it long enough.
• If you have oven-safe bowls or mugs, you can fill each with soup, then top with a slice of bread. Sprinkle on Gruyere or Parmesan cheese, and run under the broiler until the cheese is melted and the bread is toasty. Dunk the bread into the soup as you eat.