This fancy-sounding soup is actually a humble dish that has sustained its popularity because it delivers dynamite flavor from only a few cheap ingredients, it's easy to make and it's even low-fat, assuming you don't drown it in cheese. In fact, the soup is so flavorful that it can easily stand on its own, without the customary crouton and melted Gruyère. Sans cheese, a small serving fits well as part of a multi-course meal.
In making this soup I turned to James Peterson's excellent volume, Glorious French Food (Wiley, hardcover, $45), in which he presents several onion-derived soups, including the one I used as the basis for this soup. Here I've cut the recipe in half and made some minor changes but the credit still goes to Peterson.
With so few basic ingredients, French onion soup is remarkably versatile. You should feel free to experiment and make substitutions as long as you follow the basic procedure. I happened to have goose fat on hand so I used it to sauté the onions but you could also use canola oil, butter or olive oil. Because the recipe calls for so little fat, it's probably safe to choose your fat based on flavor.
Beef stock is probably the most common base for this soup but feel free to choose whichever kind of stock you like, knowing that the dominant flavor will still be onion. It's cheaper to buy a small jar of concentrated bouillon paste than it is to buy stock in cans. Look for one without MSG and with relatively low sodium.
2 tablespoons butter, oil or fat
5 cups beef or vegetable stock
1 tablespoon dried thyme and 1 bay leaf or 1 tablespoon herbes de Provence
1/3 cup vermouth or dry white wine (optional)
Kosher salt (if necessary) and freshly ground black pepper
1 baguette, sliced into 3/4-inch thick rounds
Grated Gruyère cheese
1) Put on goggles. Slice onions as thinly as possible
2) In a large, wide pot, melt butter, oil or fat and add onions. Stir occasionally until onions soften and release liquid, about 15 minutes.
3) Turn heat to high to evaporate liquid and encourage onions to brown (but not burn), about 15 minutes.
4) Meanwhile, pour stock into a large saucepan. Add herbs whether loose or in cheesecloth or tea ball. Bring stock to a boil and then turn off heat. Do not remove herbs until step 7.
5) Turn heat back down to medium and allow all of the liquid to evaporate, another 10-20 minutes. You should have lots of onions and nice, glossy brown goo stuck to the bottom of the pot.
6) Add vermouth (if you have it) or 1 cup of stock and turn heat to high. Stir vigorously to loosen browned bits from the bottom of the pan.
7) When the broth has completely evaporated and the onions are browned and stuck to the pan again, add the rest of the broth and scrape the bottom of the pan to loosen all of the browned bits.
8) Bring the soup to a boil, reduce heat and simmer 10 minutes.
9) Taste and season with salt and pepper.
10) To serve with bread and cheese, first toast the bread rounds for 20 minutes at 400° F. Ladle soup into bowls, top with 1 round of bread and grated cheese. Bake until cheese is bubbly and light brown.
When onions are chopped they release sulfuric vapors that irritate the eyes and, to a lesser degree, the nasal passages. There's really only one way to prevent the fumes from making you cry like a little girl: Don't let them reach your eyeballs. Though contact lenses do help, the best method is to wear goggles, whether they're for working with power tools, skiing or swimming. My personal preference is swim goggles simply because they are definitely not vented (as many ski and shop goggles are), therefore blocking virtually all of the evil vapors. Sure, you look like a dork but who cares.
Slicing several pounds of onions doesn't actually take that long, assuming you've got your eye-protection in place and a sharp knife in hand. Don't be tempted to use a food processor for this recipe—it won't slice the onions thinly enough. Using a mandoline or a Japanese vegetable slicer would be quick and effective.
Peterson recommends using red onions because they are moderately sweet. The very sweet Vidalia, Maui or Walla Walla onions are relatively expensive and their sweetness would likely be wasted on this soup.
You can also use this recipe (stop before adding the stock) simply to make caramelized onions. Use them for homemade pizzas, in sandwiches, on top of pork chops or bruschetta, in quiches and omelets. Divide the total amount into smaller portions and toss them into the freezer for future use.