Bistro French Onion Soup

Name: Bistro French Onion Soup
Prep time: 10 min
Cook time: 105 min
Ingredients: 3 tablespoons salted butter; 1 tablespoon olive oil; 10 cups sweet onions (from about 6 onions sliced into half moons); 1 1/2 teaspoons fine kosher salt; 2 cloves garlic (finely minced); 1/2 cup dry white wine (Sauvignon blanc, Pinot Grigio, Chardonnay); 1 tablespoon all-purpose flour; 8 cups beef broth; 1 teaspoon Worcestershire sauce; 1 tablespoon fresh thyme (plus more for serving); 1 bay leaf; 1 medium French baguette; 2 tablespoons olive oil; 8 ounces gruyére cheese (freshly grated)

Jump to Recipe

This simple Bistro French Onion Soup is beyond comforting. With deeply caramelized sweet onions in a savory thyme-infuse broth and topped with homemade bread cubes and freshly grated gruyére cheese, you’ll feel just like you’re tucked into a tiny bistro on the streets of Paris enjoying a hearty bowl of their famous soup.

Two bowls of French onion soup with sprigs of thyme and bread cubes all around with extra bowls in the background.

What You’ll Love!

Simple ingredients come together to create this immensely flavorful soup
The broth can be made a head of time and actually tastes better the next day
Freshly toasted French bread cubes and melty gruyére cheese make this soup hearty and satisfying

Ingredient Notes

Sweet Onions – Look for onions labeled as Vidalia or sweet onions. These onions have more sugar than yellow onions and the sweetness will really come out as they cook.

Dry White Wine – Wine helps to deglaze the pan and further caramelize the onions. I recommend using Sauvignon blanc, Pinot Grigio, or Chardonnay. Remember, the rule of thumb is if you won’t drink it don’t use it to cook with so avoid using cooking wines.

On that note, if you don’t drink at all, simply replace the wine with more broth.

Flour – Adding just a bit of flour will help create a silkier broth.

Beef Broth – I use regular full-sodium beef broth in this recipe. If you use low-sodium broth you’ll likely need to add more salt. Taste as you go and adjust the seasonings to your taste.

Baguette – I use a baguette to make my croutons but any crusty bread, like French or Italian bread, will do.

Gruyére Cheese – Gruyére adds a salty component that nicely balances the sweetness from the onions and the savoriness of the broth. As always, I recommend freshly grating the cheese for optimum melty goodness.

Step By Step Instructions

Note: Full list of ingredients, their amounts, and instructions can be found in the recipe card below.

Step 1:

In a large Dutch oven or stockpot, heat butter and oil over medium heat until the butter has melted.

Four part grid showing the steps of caramelizing the onions, adding the garlic, adding the flour, and then adding the broth and seasonings.

Step 2:

Add the sliced onions and salt and toss to coat in the butter and oil mixture. Continue cooking the onions, stirring occasionally, over medium heat until they become deeply caramelized. This should take about 1 hour.

Note: If the onions are caramelizing too quickly or are beginning to burn, reduce the heat a bit. However, if after about 30 to 40 minutes the onions are still fairly light in color, you may need to turn the heat up a bit.

Step 3:

Add the minced garlic and sauté for another 5 minutes.

Step 4:

Pour in the wine and stir to combine with the onions, scraping up any bits that are stuck to the bottom of the pot. Allow it to simmer for 5 minutes.

Step 5:

Add the flour and cook, stirring often, for 1 minute.

Step 6:

Pour in the beef broth, Worcestershire sauce, fresh thyme, and the bay leaf. Gently simmer the soup, covered, for 30 minutes.

Step 7:

While the soup is simmering, preheat the oven to 400 degrees F. Cut the baguette into 1-inch cubes and lay them out on a baking sheet. Pour the olive oil over the bread and toss to coat. Bake for 8 to 10 minutes or until they are crispy and golden brown.

Step 8:

Two images showing topping French onion soup with bread cubes then topping it with shredded cheese.

Remove the bay leaf from the soup.

Place broiler-safe soup bowls on a sturdy baking sheet. Top each one with some of the bread cubes. Then, top them with the grated gruyére cheese. Broil for 3 to 5 minutes or until the cheese is bubbling and beginning to brown. Top with extra thyme to serve.

Up close shot of a bowl of French onion soup with a spoon and bread cube on the plate next to it.

Items You May Need

You’ll need bowls that are broiler-safe. I used these French Onion Soup Bowls with handles.

Tips & Tricks

Place the bowls on a sturdy baking sheet to broil them in the oven. This makes transferring them much easier.
When placing the bread cubes on top of the soup, try to make an even layer and completely cover them with the cheese. Pieces sticking up may char and even burn while broiling.
You can make the broth ahead of time and store it in the fridge until you are ready to use it.

Storage & Reheating

Only make enough servings as you need them. The bread will absorb the soup and become soggy so it should be stored separately from the broth.

Keep extra soup in an airtight container in the fridge for 3 to 4 days. It can also be kept frozen for up to 6 months.
Keep the bread cubes in an airtight container on the counter for up to 1 week.
Grate the cheese as you need it.
When you want to serve the soup, reheat the broth. Then top with the bread and cheese and broil.

Recipe FAQ’s

Can I use any type of onion?

Any onion will work but they will alter the taste a bit. Red onions are sweet like Vidalia onions. Yellow onions are less sweet and you may find that you want to add a teaspoon of sugar while the onions are cooking to increase the sweetness.

Do I have to use gruyére cheese?

Not at all! Feel free to switch it up. Swiss cheese will be the most similar in flavor but you could also use provolone, mozzarella, fontina, or gouda cheese.

Can I make this soup vegetarian?

Sure! The beef broth can be replaced with vegetable stock or broth. The Worcestershire sauce can be replaced with a vegetarian Worcestershire sauce or you can use soy sauce or coconut aminos instead. You’ll also need to use a vegetarian cheese as most gruyére cheese contains rennet.