Somewhere between a starter and a full meal lies French onion soup gratinée. Here's how to make it at home.

By Jackie Freeman
September 30, 2020
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This French country classic is the perfect mixture of sweet caramelized onions and savory beef broth, and the whole thing is topped with a crusty piece of bread draped with cheese melted until golden brown and bubbly.

It's the final step of baking cheese over the top that makes the recipe "gratinée." I'll take you through each step of making French onion soup and share simple how-to tips, plus recipes made on the stovetop, slow cooker, and Instant Pot.

1. Caramelized Onions

Onions sliced for caramelized onions
Stirring Caramelized Onions

Don't cry over these sliced onions, they just might be the most important part to French onion soup! Ideally, you want to reach for sweeter varieties, like Walla Walla onions or Vidalias. Or, you can use a combination of sweet onions and regular yellow onions. If all you have available are yellow onions, you can boost the sweet flavor by adding a splash of balsamic vinegar or a pinch of brown sugar after the onions have been caramelized. Cut your onions in half, and then cut each half into thin slices.

  • Tip: When caramelizing onions, low and slow is the way to go. Make sure to take your time and cook the onions over low heat, so that the natural sugars caramelize instead of burn. If you're doing it right, this should take 30 to 40 minutes. Make sure to stir the onions often and scrape the pot with a wooden spoon to keep all of those tasty browned bits on the bottom from burning.
  • Tip: When you're combining the onions and broth, pour a bit of broth into the hot onion pan and scrape up the browned bits to add to the soup.

2. Broth

Two mason jars of clear amber-colored stock
Credit: France C

Beef stock or broth forms the base of this soup to make it rich, savory, and hearty. It's the perfect complement to the sweet caramelized onions. If you're looking for a slightly lighter fare, you can swap out the beef with chicken or vegetable stock, or broth. Either make your own beef bone broth or chicken broth, use condensed broth mixed with water, or pop open a box of stock and skip the water. If you are using canned or boxed broth, you can fancy it up by simmering it with a few fresh herbs, a bit of miso paste, aromatics (like peppercorns or whole cloves of peeled garlic), or even a Parmesan cheese rind. Make sure to strain it first, before adding it to your soup!

  • Tip: Adding a splash of wine gives the soup a nice "pop" from the acid. If you don't have a bottle of red on hand, you can use white wine, red or white wine vinegar, cognac, sherry, or even a splash of brandy!
  • Tip: Want to add even more flavor? Add a few fresh sprigs of thyme or rosemary, or a few bay leaves to your simmering soup.

3. Bread

French Baguettes
Credit: Katty Loan Chu

Slices of French baguette form the base of the classic topper for French onion soup gratinée: crusty bread and melted cheese. And, if your bread happens to be slightly stale, that's even better! A lightly toasted or slightly stale piece of bread will absorb just enough of the broth without becoming a soggy mess by the time the soup is on the table.

  • Tip: No baguette on hand? Reach for other crusty counterparts, like Italian bread, stale croissants, or even store-bought or homemade croutons. Just make sure to cut them to fit snugly in your bowl.

4. Cheese

Cheese is the other half of the topper for French onion soup gratinée. Traditionally, you'd use Gruyère cheese, which is similar to Swiss but with a slightly milder and nuttier flavor. You can also use Swiss cheese, which is easy to find at many grocery stores. If Swiss isn't your preferred slice, feel free to swap it out with other cheeses you like, or happen to have on hand. Grated Parmesan, shredded or sliced mozzarella, softy and creamy Brie, Havarti, or Gouda — or a combination of any of those — make great substitutions.

  • Tip: Slice or shred? Some like the simplicity of a slice of cheese on top of their soup. It creates a nice "lid" to the dish and doesn't make much of a mess. However, if you're looking for some authenticity (and amazing flavor), choose grated cheese. It will fall into the soup and melt, resulting in delicious melty strands of cheesy-goodness with every bite.
  • Tip: For easy serving, place individual oven-proof bowls on a baking sheet and fill with soup. Top with toasted bread and shredded or slice cheese. Slide the baking sheet under the broiler for 3 to 5 minutes, just until the cheese is melted and bubbly, with a toasted golden crust.

5 Ways to Make French Onion Soup

  1. Slow Cooker French Onion Soup : Caramelized onions are simmered in broth all day, and the soup is finished under the broiler for a classic gratinée.
  2. French Onion Soup Gratinée: This stovetop version uses a combination of chicken and beef broth.
  3. Instant Pot French Onion Soup: Convenient, yes, but you'll want to give the onions more time to caramelize to get the color and flavor that are are the hallmarks of French onion soup.
  4. Vegan French Onion Soup: A classic preparation, but with vegan-friendly ingredients.
  5. French Onion Soup I: Made on the stovetop, with a bit of flour to thicken the soup slightly.

Get more French Onion Soup recipes.

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