Classic French Onion Soup is a perfect union of sweet caramelized onions, crusty french bread croutons, and bubbly melted cheese. Our tried-and-true, easy-to-make recipe is rich, savory, and satisfying to the bone.
What's the Story on this Recipe?
Classic French Onion is a simple soup made of four basic components - sweet caramelized onions, savory stock, crusty french bread, and bubbly melted cheese.
The modern version of French Onion Soup dates back to 18th century Paris, where it was a favorite of King Louis XV. It was first introduced to the United States in 1861, by New York restaurateur Henri Mouquin (or more likely, by his chef-wife Marie). In the 1960s, it again gained popularity, inspired by celebrity chef Julia Child, and the Kennedy White House's interest in French cooking.
Because of its ease of preparation and dependably delicious results, this easy French Onion soup recipe is one you will want to keep in regular rotation. If you make the caramelized onions ahead of time, it can be on the table in less than 30 minutes!
What Goes into this Recipe
All About Onions
The type of onions you use can dramatically impact both the cooking time and the sweetness level of your soup. It may seem counterintuitive, but avoid using sweet onions for caramelizing.
When making anything with caramelized onions, I prefer to use a mixture of red and yellow onions. Sweet onions will work, but will take significantly longer to cook, and the end-product will have less flavor than that made with red and/or yellow onions.
You might be wondering what causes the aforementioned Onion Sweetness Inversion, so here's the scoop: plain old red and yellow onions have a far more complex flavor profile than do sweet onions.
While we perceive sweet onions to be sweeter, yellow and red onions have more pungent lachymators (i.e., stuff that makes you cry) than do sweet onions (e.g., WallaWallas, Vidalias, etc.), giving the impression that the red and yellow onions have a higher sugar content, when the opposite is actually true.
It is because of their higher sugar content that red and yellow onions yield richer caramelized onions, and subsequently, more flavorful French Onion Soup.
The Best Cheeses for French Onion Soup
Traditionally, French Onion Soup is topped with a bubbly, broiled Gruyère cheese. Gruyère is a Swiss-type or Alpine cheese.
Gruyère has a distinctive but not overpowering taste and gets excellent scores for meltability. The flavor of Gruyère can vary wildly, depending on both cheesemaker and age. Like Jarlsberg, young Gruyère is described as creamy and nutty, with the later becoming more earthier as it matures. Fully aged Gruyère can have a slightly grainy texture, like that of aged cheddar.
Depending where you live, it can be difficult to find good Gruyère. If you have this problem, do not - for the love of all Kitchen Elves everywhere - do not buy anything with the words "processed" in its name to melt on top of your hard-earned caramelized onions (unless you enjoy eating melted Play-doh). Instead, go with one of these delicious alternatives.
Gruyère Cheese Substitutes
Fontina and Parmesan: In the absence of Gruyere, the Fontina & Parmesan combo is my personal favorite cheese finish for French Onion Soup. (The soups shown throughout this post are all topped with this mixture.)
Fontina is a semisoft, very meltable cheese with a slightly nutty, savory flavor. Fontinas from the United States usually have a milder flavor and softer texture than do those from Europe. I don't think I'd use a European Fontina for this soup.
Jarlsberg: Jarlsberg is my favorite everyday cheese. It's smooth, sweet, nutty flavor complements French Onion Soup and pulls the sweet notes from the soup. Really good choice. (The only reason I list Fontina first is because, objectively, as far as flavor and meltability are concerned, it is more closely aligned with Gruyère.)
In a pinch, any mild, meltable Swiss cheese will work. Just choose a cheese you love, grate it up, and enjoy!
Baguette or Batard
French baguettes are the usual crouton of choice for French Onion Soup; however, I prefer to use French Batard.
What the heck is a batard, anyway?
A batard is the lesser known cousin of the thin, sexy French baguette. Usually about a foot or less long, the batard is much thicker around than the baguette, with a slightly thinner crust. I find that batard croutons make for a better soup-eating experience: they are easier to spoon up, and not quite as chewy as those made from baguette rounds.
No fancy french breads? No worries! Everyday grocery-store French bread will also work just fine. Your choice of bread for the croutons is totally up to you.
A soup is only as good as the stock upon which it is built.
French Onion soup is traditionally made with beef stock (or broth); however, you can make it with chicken or vegetable stock if desired.
If you make your own soup stock, use a light version. You don't want the flavor of your stock to overwhelm the subtleties of the caramelized onions.
You should be able to see sunlight through a jar of your stock. If it is too thick to see the light, add a little water, or a 75/25 combination of water and wine.
Always taste any stock, including boxed stocks, before you use them. A bad stock can ruin an entire soup; a great one can elevate it. If you don’t like the flavor of your stock, don't use it.
Additional Ingredient Notes & Substitutions
- Wine: Many people prefer a dry white wine works best for French Onion Soup; Pinot Gris, Sauvignon Blanc, Semillon, or Chardonnay. We like our French Onion Soup slightly lighter and on the sweet side: a good Reisling works very nicely for that.
- If you are not a wine-drinker and prefer not to buy it, you can use equal parts additional broth and white grape juice in place of the wine.
- Worcestershire: If your soup is missing something, add an additional tablespoon of Worcestershire sauce and see if that does the trick.
- Thyme: If you can find it, use fresh thyme. It really does make a difference.
- If you can't find fresh, you can substitute 1 teaspoon of dried thyme for each tablespoon of fresh.
- Flour: You can use all-purpose flour, however, we recommend using Wondra.
- Wondra, or instant flour, dissolves more quickly than all-purpose flour, and mixes into both hot and cold liquids easily. This makes it particularly useful for making smooth, creamy, lump-free sauces and gravies as well.
- Garlic: Don't overdo it, or the garlic will overwhelm you soup.
- Olive oil: Use a light flavored olive oil. Canola oil is a good substitute.
- Butter: We always recommend using real butter, never margarine.
How to Make this Recipe
Foolproof step-by-step directions for caramelizing onions can be found on our post, Slow Cooker Caramelized Onions.
In a 10-inch Enameled Cast Iron Dutch Oven (or other large, heavy-bottom saucepan) melt 2 tablespoons olive oil and 2 tablespoons butter over medium-low heat.
Add sliced red or yellow onions to melted oil and butter.
Cook slowly, stirring frequently, over medium-low heat until onions are very soft and have turned dark golden brown.
Caramelizing the onions should take at least 45 minutes. DO NOT RUSH or your onions may turn out bitter.
TO USE PRE-PREPPED CARAMELIZED ONIONS (which we heartily encourage you to do!):
Skip the step outlined above and just add 2 cups (16 ounces) pre-prepped caramelized onions to the Dutch Oven.
Heat over medium-low until the onions are bubbly; about 5 minutes.
Taste the onions before proceeding. If they don't seem as sweet as you'd like them. to be, stir in just a pinch of sugar and see if that does the trick.
To the prepared caramelized onions, add the wine and deglaze the pan.
If you prefer to avoid cooking with alcohol, you can use equal parts additional broth and white grape juice in place of the wine.
Bring to a simmer over medium-low heat. Stir in garlic, thyme leaves (or dried thyme), and freshly ground pepper.
Reduce the heat and simmer on low until the wine has evaporated and the onions are nearly dry; about 5 minutes. Add the beef stock and Worcestershire sauce.
Return soup to heat and allow to simmer 10 minutes more. Season to taste.
While soup is simmering, arrange baguette slices on a baking sheet in a single layer. Set under broiler just long enough to toast lightly; about 2 minutes.
Flip the baguette rounds over and repeat.
Rub one side of each toasted bread slice with a clove of garlic.
When you are ready to serve, ladle hot soup into oven-safe bowls. Float one or more prepared baguette croutons on top. Sprinkle generously with grated cheeses.Place under broiler just long enough to melt and slightly brown the cheese.
No need to worry about fancy soup crocks if you don't have them: you can serve French Onion Soup in any individual, oven-safe vessel. Garnish with a sprig of fresh thyme and you're all set!
FAQs & Expert Tips
Browning is the relatively quick process of browning the outside of onions, done in hot oil at relatively high temperature.
Caramelizing, on the other hand, is a much slower process; requiring no less than 45 minutes (and upwards from an hour for larger quantities) over much lower heat.
Caramelization describes the chemical reactions that take place when any sugar is heated to the point that its molecules begin to break apart and generate hundreds of new flavor, color, and aroma compounds. (Cook's Illustrated)
This slow cook is necessary in order for the chemical process to occur that transforms the sugars in the onions into rich, jammy, umami goodness. This magical transformation only happens after a long cooking time. The more caramelized, the deeper will be the color of the onions and the more intense the flavor.
You can encourage the caramelization process by adding a teaspoon or two of sugar to the onions as they cook; however, the process cannot be rushed. Doing so may result in bitter onions; and subsequently, bitter soup.
Using the traditional stove-top method, caramelizing the onions for this French Onion Soup recipe will take at least 45 minutes, and up to an hour. (I make caramelized onions in the slow cooker, over a period of about 18 hours.)
You wouldn't think so, but apparently, it does.
According to America's Test Kitchen, slicing onions from pole to pole (root to stem) instead of cross-grain prevents them from breaking down too much during the long cooking process.
TIP: Did you know you can freeze caramelized onions? Make a big batch and freeze them. Then you can have this easy-to-make soup on the table in just 30 minutes, anytime you want!
I'm not big on excessive kitchen gadgets, but this herb stem stripper is a thumbnail saver - and totally worth the real estate it takes up in my kitchen drawer.
To use it, you just thread the stem through the smallest hole through which it will fit, and pull the stem through. Like magic, the herb leaves fall away, ready to use. It works like a charm on fresh thyme!
Mr B and I prefer our French Onion Soup on the lighter side of traditional, both in sodium load and flavor profile.
You can lighten this soup recipe by substituting a light chicken stock or vegetable stock in place of the traditional beef broth base, and white wine instead of the customary red or port.
Note that if you sub in a vegetable stock, take care that it doesn't have a strong flavor, as it will affect the outcome of your soup.
If you prefer the classic, intensely flavored French Onion Soup, use beef broth and red wine as listed in the recipe.
Classic French Onion Soup
- 5 pounds red or yellow onions about 4-5 large onions, sliced stem to root about ¼" thick (use pre-prepped caramelized onions)
- 2 tablespoons butter
- 2 tablespoons olive oil
- 2 cloves garlic minced
- 1 tablespoon fresh thyme minced (or ½ teaspoon dried thyme), plus a few sprigs for garnish
- ½ teaspoon freshly ground pepper
- 2 tablespoons Wondra or all-purpose flour
- 1 cup red wine or white wine
- 4 cups beef stock or chicken stock, or vegetable stock
- 2 teaspoons Worcestershire sauce
- 6 ounces Gruyere grated; or Fontina, Swiss, or Provolone
- 1 ounce Parmesan shredded or grated; optional
- 2 cloves garlic whole, peeled
- 1 french bread baguette or batard or french bread loaf; sliced in ½-inch rounds
- salt to taste
- In a 10-inch Enameled Cast Iron Dutch Oven (or other large, heavy-bottom saucepan) melt 2 tablespoons olive oil and 2 tablespoons butter over medium-low heat. Add sliced red or yellow onions to melted oil and butter.Cook slowly, stirring frequently, over medium-low heat until onions are very soft and have turned dark golden brown. Caramelizing the onions should take at least 45 minutes. DO NOT RUSH or your onions may turn out bitter.Foolproof step-by-step directions for caramelizing onions can be found on our post, Slow Cooker Caramelized Onions.
- To the prepared caramelized onions, add the wine and deglaze the pan. Bring to a simmer over medium-low heat. Stir in garlic, thyme leaves (or dried thyme), and freshly ground pepper. Reduce the heat and simmer on low until the wine has evaporated and the onions are nearly dry; about 5 minutes.
- Add the beef stock and Worcestershire sauce.Return soup to heat and allow to simmer 10 minutes more. Season to taste.
- While soup is simmering, arrange baguette slices on a baking sheet in a single layer. Set under broiler just long enough to toast lightly; about 2 minutes. Flip the baguette rounds over and repeat. Rub one side of each toasted bread slice with a clove of garlic.
- When you are ready to serve, ladle hot soup into oven-safe bowls. Float one or more prepared baguette croutons on top. Sprinkle generously with grated cheeses. Place under broiler just long enough to melt and slightly brown the cheese.
- Garnish with fresh thyme sprigs and serve.
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Recipe Updated February 9, 2021 (Originally published November 21, 2013)