The best French Onion Soup Recipe starts with the right onions and develops a hearty broth. Topped with cheesy toast.
I recently ordered a bowl of French Onion Soup at a favorite local pub that for years has been known for theirs. What I got was a thick layer of melted cheese on a slice of bread that had soaked up most of the broth underneath with a scant serving of onions. Maybe it was just a bad night, but I was left unsatisfied… and this experience sent me on a mission: Find the best French onion soup recipe that I can make at home. After some trial, error, and disappointment, success is mine. Also,French Onion Soup is an excellent recipe to master, being one of the classics for a pleasing meal.
This recipe comes from America’s Test Kitchen and I should have just gone there first. They do all the research; testing several types of onions as well as coming up with the best cooking methods. I mean, they are the TEST kitchen. The success of this recipe is based on creating a deep, crusty caramelization with the onions, also known as fond. After following this recipe (courtesy of Christopher Kimball’s house guest from France), this is the best French onion soup I’ve tasted.
How to make French Onion Soup-
The recipe requires a bit of pre-planning but it’s extremely easy. You do need to start early, and monitor it periodically until the active hands-on portion during step three of the printable recipe.
Start with about six large yellow onions, sliced pole to pole. See note below on crying over your onions. Do not use sweet, white or red onions. They each have less than stellar results. So, nice round yellow onions it is for this recipe. After the onions are sliced (not too thinly), spray a heavy bottomed pot (at least a 7 quart size) with cooking spray (cast iron is what I use), place butter in the bottom and fill it with your onions. You will add a bit of salt here to help sweat the onions. Cover and cook in a 400 degree oven for an hour. Your house will start to smell amazing right about now.
Here they are after the first hour in the oven. Those onions that totally filled your pot have started to sweat down and are beginning to caramelize to the sides of the pan. Give them a good stir, crack the lid about an inch, and put them back in for another 1 1/2 to 1 3/4 hours, stirring again after one hour.
Now there is a heavy crust (the fond I mentioned earlier) that is starting to form and your onions are totally reduced. At this point, you’re going to cook them on the stove top, to draw out more of the moisture and deglaze the fond from the pan.
You will add water and deglaze at least three times as the onions continue to brown. The crust is THE flavor that makes this French onion soup recipe stand out, and you have perfectly caramelized onions. The crust also helps create a thick broth that doesn’t require the use of flour.
The deglazing portion was really the only active part of this recipe. Now you need a little bouquet of thyme sprigs and a bay leaf. Add this with your cooking sherry, chicken broth*, beef broth and water. Simmer on the stove top for 30 minutes. Finish off under the broiler with toasted, sliced baguette and shredded Gruyère.
This soup is super hearty and flavorful. My quest is complete. I hope you agree.
What type of broth to use in French Onion Soup-
I’ve had people ask me why not just use beef broth here, assuming the beef broth will give deeper flavor. But that is not the case. This is French ONION Soup. Using chicken broth allows for the onions to shine in this soup. Trust me, the soup will have the perfect depth of hearty flavor. That being said, this makes a fine soup if you want a vegetarian option. Substitute in good vegetable broth.
What type of onions are best in French Onion Soup-
Yellow onions are most often recommended for French Onion Soup. They provide the perfect flavor that isn’t too sweet (white and red are both sweeter than yellow). Also, besides being too sweet, red onions really don’t look appealing in an onion soup such as this. The color turns to a purple-y grey.
A little note on “crying over your onions”. Many of us cry when slicing onions. It just happens. And the reason it happens is there are certain enzymes in onions that, when cut, release a sulphuric acid which irritates your eyes. There are many supposed remedies to prevent crying (light a candle, bite on a wooden spoon, freeze the onions). But the simple method that is tried and true: Protect your eyes. There are actually “onion goggles” out there you could buy, but just put on a pair of safety goggles or even swim goggles if you want ultra protection. Then you’ll look like you really mean business and you’ll stay dry-eyed through all 6 onions! 🙂
Best Cheese for French Onion Soup-
Gruyère cheese is not only a good classic cheese for French Onion Soup, it’s so rich in flavor that I think it makes the soup. But mozzarella, Swiss cheese, and provolone are adequate substitutes. If not using the strong Gruyère cheese, I recommend sprinkling Parmesan cheese over any of the other options to bump up the salty flavor of the cheese.
French Onion Soup
For the Soup:
- 3 Tablespoons unsalted butter, cut into 6 pieces
- 6 large yellow onions, about 4 pounds, halved and cut pole to pole into generous ¼-inch-thick slices. Be sure to weigh the onions to get the right amount.
- 1 teaspoon salt
- ½ cup dry sherry
- 3 cups low-sodium chicken broth
- 3 cups beef broth
- 2 cups water, plus extra for deglazing
- 4-6 sprigs fresh thyme, tied with kitchen twine (Don't overdo it here)
- 1 bay leaf
- ½ teaspoon sea salt
- Ground black pepper
For the Cheese Croutons:
- 1 small baguette, cut into ½-inch slices (If making gluten free, omit bread or better yet, use a hearty gluten free bread, like Udi's)
- 8 ounces shredded Gruyère cheese, about 1 cup. Mozzarella can be substituted.
- For the soup:
- Adjust oven rack to lower middle position and heat oven to 400 degrees. Generously spray inside of heavy-bottomed large (at least 5-quart) Dutch oven with nonstick cooking spray. Place 3 Tablespoons butter in pot and add 6 cut onions and 1 teaspoon salt. Cook, covered, 1 hour (onions will be moist and slightly reduced in volume). Remove pot from oven and stir onions, scraping bottom and sides of pot. Return pot to oven with lid slightly ajar (only about ½-inch open) and continue to cook until onions are very soft and golden brown, 1 ½ to 1 ¾ hours longer, stirring onions and scraping bottom and sides of pot after 1 hour.
- Carefully remove pot from oven and place over medium-high heat. Using oven mitts to handle the pot, cook onions, stirring frequently and scraping bottom and sides of pot, until liquid evaporates and onions brown, 15 to 20 minutes, reducing heat to medium if onions are browning too quickly. Continue to cook, stirring frequently, until pot bottom is coated with dark crust, 6 to 8 minutes, adjusting heat as necessary. (Scrape any fond that collects on spoon back into onions.) Stir in ¼ cup water, scraping pot bottom to loosen crust, and cook until water evaporates and pot bottom has formed another dark crust, another 6 to 8 minutes. Repeat process of deglazing with water 2 or 3 more times, until onions are very dark brown (very). Stir in ½ cup sherry and cook, stirring frequently, until sherry evaporates, about 5 minutes.
- Stir in 3 cups chicken broth and 3 cups beef broth, 2 cups water, 4-6 sprigs of thyme, 1 bay leaf, and ½ teaspoon salt, scraping up any final bits of browned crust on bottom and sides of pot. Increase heat to high and barely bring to boil. Reduce heat to low, cover, and simmer 30 minutes. Remove and discard herbs, then season with salt and pepper.
- For the croutons:
- While soup simmers, arrange baguette slices in single layer on baking sheet and bake in 400-degree oven until bread is dry, crisp, and golden at edges, about 10 minutes. Set aside.
- To serve:
- Adjust oven rack 6 inches from broiler element and heat broiler. Set individual broiler- and oven-safe bowls on a baking sheet and fill each with about 1 ¾ cups soup. Top each bowl with 1 or 2 baguette slices (do not overlap slices) and sprinkle evenly with 8 oz Gruyère. Broil until cheese begins to melt and is bubbly around edges, 3 to 5 minutes. Let cool 5 minutes before serving.
Recipe adapted from America’s Test Kitchen.