Classic French Onion Soup

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.

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• Classic French Onion Soup

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. 

Soup Stock

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

Caramelized Onions

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.

Soup Base

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.

Croutons

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.

Serve

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! 

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Recipe Updated February 9, 2021 (Originally published November 21, 2013)