This traditional French Onion Soup recipe has warm baguettes topped with hot, melted Gruyere cheese. High quality beef broth, a splash of wine, and perfectly caramelized onions are the secrets to this classic recipe. PLUS, check out how you can prepare this recipe in the Crock Pot.

Two slices of baguette with melted cheese in a bowl of french onion soup and thyme on top.

French Onion Soup

In case you didn’t know, I am a soup fanatic. And there are so many different ways there are to make a traditional, homemade french onion soup recipe.  I have tried them all, I’ve researched a lot, and I’ve finally got this recipe totally nailed down.

The secret to making the best French Onion Soup is to properly caramelize the onions and to use high-quality ingredients. That means using good butter, wine, broth, fresh baguettes, and cheese.

But don’t worry- I’ve offered great substitution options if you prefer not to use alcohol or would like more budget-friendly cheese options. I’ll even show you how the Slow Cooker can help you caramelize those onions!

Here are all of my KEY tips on making this recipe:

 

Use a Combination of Yellow and Sweet Onions

  • Each type of onion adds a different element of flavor. Combining the two allows you to enjoy the best of what each has to offer.
  • I like to use 2 sweet (vidalia) onions and 4 yellow onions, they weigh a solid 5 pounds total.
  • Use a madoline slicer to cut the onions quickly and evenly.

Use Dry White Wine

  • I have tried several different wines for this recipe and I find dry white wine to be the best.

Best Dry White Wines for Cooking:

  • Sauvignon Blanc
  • Pinot Grigio
  • Unoaked Chardonnay

If you prefer to make this without wine:

  • You can substitute 3 Tablespoons white wine vinegar + chicken or beef broth to make 3/4 cup.

Best Cheese For French Onion Soup

  • Gruyere cheese is best.
  • Other cheese options include Comte, Emmental (Swiss), Provolone, or Mozzarella.

Use High Quality Beef and Chicken Broth

How to Caramelize Onions

Caramelizing onions is very easy, it takes patience more than skill. Follow the simple steps below and the rest will take care of itself.

Don’t cut the onions too thin

  • You want 1/4 inch slices, as they will shrink down and you don’t want them to be too thin or stringy.

Coat the onions generously in butter.

  • Use a set of tongs makes them easy to toss around in the pot.

Cook them low and slow

  • Cook the onions over medium-low heat. This process takes some time but the end result is well worth it.

Use more onions than you think

  • Onions made up of over 80% water. They shrink down considerably as they cook, as you will see below.
  • I use 5 pounds in this recipe.

Watch These Onions Caramelize. Each photo was taken 20 minutes apart.

Onions in a soup pot that are freshly cut and beginning to cook down in order to make French Onion Soup.

Onions in a soup pot for French Onion Soup that are beginning to soften. Onions in a pot that are beginning to caramelize and turn a light brown. Step by step photos of how to caramelize onions, this is the end of process where they are caramelized and brown.

Caramelizing Onions in the Crock Pot

The benefit of caramelizing the onions in the Crock Pot is that you don’t have to stir them while they reduce and you can get most of the work done overnight. They’ll need to cook on low for 10 hours.

Note: To fully caramelize them, you will need to transfer them to a pot on the stove at the end with some additional butter and some of the juices from the Crock Pot over medium-high heat for 10-15 minutes. You will then finish the soup on the stove top as well.

  • Melt 4 Tablespoons of butter in the Crock Pot. Add the onions and toss to coat. Cook on low for 10 hours.
  • Melt 2 Tablespoons of butter in a large pot on the stove over medium-high heat. Wait until it begins to foam. Add the onions and cook for 10-15 minutes.
  • Decrease heat to medium. Add the white wine and cook for an additional 2-3 minutes. Pour in the beef broth, chicken broth, Worcestershire sauce, and add the bay leaves and thyme.
  • Simmer for another 45 minutes on the stove with the lid cracked. OR, transfer back to the Slow Cooker and cook for 2-3 hours on high or 4-6 hours on low.

Instant Pot Method

Yes, it’s true! You can make this in the Instant Pot! (As featured on MSN.)

Make-Ahead Method

  • There is probably no better soup to make ahead of time than this. This soup can be stored in an airtight container for up to three days prior to serving.
  • The soup can be reheated on the microwave, Slow Cooker, or stove top, and the baguettes and cheese can be toasted/melted separately and added to the soup once ready to serve!

Freezing

This is a great freezer meal.

  • Let it cool prior to freezing and store it in an airtight container.
  • It’s best if used within 3 months of freezing.
  • Freeze only the soup, don’t include bread/cheese with it.

Overheat shot of a hand holding a white bowl filled with french onion soup topped with two cheesy baguettes.

Try These Next!

Want My Soup Crocks?

(Amazon affiliate link) I bought these oven safe soup crocks just for this soup. They’re very study, handmade, super high quality.

Check out all of my kitchen essentials here.

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A mug of French Onion Soup topped with 2 slices of cheesy baguettes.

French Onion Soup

Prep Time: 15 minutes
Cook Time: 1 hour 25 minutes
Total Time: 2 hours 55 minutes
4.95 from 98 ratings
Servings: 6
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This traditional French Onion Soup has warm baguettes topped with hot, melted Gruyere cheese. High quality beef broth, a splash of wine, and perfectly caramelized onions are the secrets to this classic recipe.

Ingredients

US Customary - Metric
  • 4 large yellow onions,, see notes for pound conversion
  • 2 large sweet onions, Vidalia
  • 6 Tablespoons butter
  • 2 sprigs fresh thyme
  • 2 Bay leaves
  • ¾ cup dry white wine, Chardonnay or Pinot Grigio
  • 3 tablespoons flour, optional
  • 4 cups beef broth, high quality is key
  • 1 beef bouillon cube, or 1 tsp Better Than Bouillon
  • 1.5 cups chicken broth
  • 1 teaspoon Worcestershire sauce
  • Salt/Pepper, to taste
  • 1 baguette
  • 3 Tablespoons olive oil, optional
  • 6 slices Gruyere cheese

Instructions

  • Slice the onions into ¼-inch slices, (no thinner). They'll reduce in size quite a bit and you don’t want them to be too stringy. (Using a mandoline slicer makes this much easier).
  • Melt the butter in a large soup pot or dutch oven over medium-low heat. Wait until it begins to foam, this allows water to evaporate out, leaving the butter more clarified and smooth.
  • Add the onions and use tongs to toss and coat them in the butter. Leave them uncovered as they cook.
  • The onions will caramelize slowly, up to 2 hours or longer. Stir them every 10-15 minutes. As the onions caramelize, they may leave some brown residue at the bottom of the pot. Add a splash of wine and use a silicone spatula to 'clean' the bottom of the pot. Repeat as needed throughout the cooking process
  • When the onions are nearly done, sprinkle flour over them and cook for 2 minutes. Add any remaining wine and increase the heat to medium-high. Toss the onions more frequently. They are done when they are richly brown and sweet.
  • Add the beef broth, beef bouillon, chicken broth, Worcestershire sauce, bay leaves and thyme. Simmer over medium heat for 45 minutes with the lid cracked.
  • While the soup simmers, preheat the oven to 350° F.
  • Slice the baguette into ½ inch thick slices. Brush the tops with olive oil and bake for about 5 minutes.
  • Increase the oven temperature to 450° F. Top each baguette with cheese and bake in the oven until the cheese melts and begins to bubble and brown.
  • Remove the bay leaves and thyme stems. Season to taste with salt and pepper.
  • Ladle the warm soup into each bowl and top each of them with the warm baguettes. Serve!

Notes

  • You should use about 5 pounds of onions (total) for this recipe.
  • If you prefer not to use Wine, you can substitute 3 Tablespoons white wine vinegar + chicken or beef broth to make 3/4 cup.
  • Other cheese options include Comte, Emmental (Swiss), and/or Provolone.

Crock Pot Method:

Note: The stove top does come into play with this method as the heat is needed to fully caramelize the onions at the end. However this method allows you to almost fully caramelize the onions overnight without stirring.
  • Melt 4 Tablespoons of butter in the Crock Pot. Add the onions and toss to coat. Cook on low for 10 hours.
  • Melt 2 Tablespoons of butter in a large pot on the stove over medium-high heat. Wait until it begins to foam. Add the onions and cook for 10-15 minutes.
  • Decrease heat to medium. Add the flour and cook for 2 minutes. Add the white wine and cook for an additional 2-3 minutes. Pour in the beef broth, chicken broth, Worcestershire sauce, and add the bay leaves and thyme.
  • Simmer for another 45 minutes on the stove with the lid cracked. OR, transfer back to the Slow Cooker and cook for 2-3 hours on high or 4-6 hours on low.
Check out my Instant Pot version!

Nutrition

Calories: 509kcal, Carbohydrates: 40g, Protein: 16g, Fat: 30g, Saturated Fat: 14g, Polyunsaturated Fat: 2g, Monounsaturated Fat: 11g, Trans Fat: 1g, Cholesterol: 61mg, Sodium: 1284mg, Potassium: 479mg, Fiber: 4g, Sugar: 10g, Vitamin A: 638IU, Vitamin C: 16mg, Calcium: 377mg, Iron: 3mg
Did you try this recipe?Mention @TheCozyCook on Instagram or tag #thecozycook!
Course: Soup
Cuisine: French
Author: Stephanie

This classic French Onion Soup has a rich, silky broth made from thinly sliced onions, butter, white wine, beef broth, fresh thyme and bay leaves. All topped with a toasted baguette and hot, bubbly Gruyere cheese. | The Cozy Cook | #soup #frenchonionsoup #onions #recipe #easyrecipes #winterrecipes #gruyere