Easy French Onion Soup with Caramelized Onions

This easy, restaurant-style French onion soup delivers rich, savory flavor and is just as good sipped straight from the bowl as it is topped with toasted bread and gooey mozzarella.

Find Comfort in This Classic French Dish

There are few things more comforting than a bowl of French onion soup slowly steaming on the table.

Traditional soupe à l’oignon gratinée often calls for pounds of onions, homemade beef broth, bay leaves, thyme sprigs, and careful attention to heat over the course of half hours or more. This recipe keeps the soul of the dish: deep golden brown caramelized onions and a savory broth, but trims it down to something realistic for everyday cooking! The most work you have to do is brown and caramelize your onions, but other than that, it’s just a matter of stirring a pot!

I love this beefy flavored soup and know you will, too. It’s the perfect way to welcome cooler temps, and a single recipe makes the perfect amount for two, but doubles, triples, and even quadruples well! You’ll also love this Creamy Root Vegetable Soup!

Ingredients You’ll Need

Unsalted butter
Sweet yellow onions, diced
Dried Basil (Optional)
Au Jus Gravy Mix
Water
Baguette bread, toasted (Optional)
Shredded mozzarella (Optional)

Helpful Tips Before You Start

Take your time with the onions. Caramelizing onions is not about high heat. Medium to medium-low heat and frequent stirring will give you the best results.
Scrape the bottom of the pan. Those browned bits are packed with flavor; don’t lose them!
Use oven-safe bowls. If you plan to broil the soup with bread and cheese, make sure your bowls can handle the heat.
Serve immediately. French onion soup is best hot, with bubbly cheese and toasted bread.

Close up of French bread being dipped into French onion soup

How to Make Easy French Onion Soup

Step 1: Caramelize the Onions

In a medium saucepot or Dutch oven, melt the butter over medium-high heat. Add the diced yellow onions and stir well to coat them in the melted butter. Cook for about 20 minutes, stirring often, until the onions are deeply caramelized and lightly browned. If using dried basil, stir it in during the last minute or two.

Step 2: Add the Broth Base

In a measuring cup, whisk together 1 cup of cold water and the packet of au jus gravy mix until smooth. Pour this into the pot along with the remaining 2 cups of water. Stir well, scraping up any flavorful bits from the bottom of the pan.

Mixing the French Onion soup mix in a bowl

Adding the French Onion soup mix to caramelized onions

Step 3: Simmer

Bring the soup to a boil, then reduce it to medium-low heat and let it simmer for about 5 minutes. Taste and adjust if needed with black pepper or a little extra water.

Step 4: Optional Restaurant-style Finish

Divide the soup into oven-safe bowls. Top each with a piece of toasted baguette and a generous sprinkle of mozzarella. Place the bowls on a baking sheet and broil on low for 3–4 minutes, just until the cheese is melted and lightly golden brown.

Adding a French Baguette to the French Onion Soup

A bowl of French Onion Soup with French Baguette topping next to a baguette

What to Serve with French Onion Soup

This soup makes a great side dish, but it’s hearty enough to stand alone. Serve it with a simple green salad, a grilled roast or drip beef sandwich, or alongside roasted chicken. It’s also perfect with some homemade rolls on a chilly night when soup just sounds right!

Storage & Leftovers

Let any cooled soup come to room temperature, then store it in an airtight container in the refrigerator for up to 3 days. Reheat gently on the stove over medium-low heat. Add fresh bread and cheese when serving for the best results.

Frequently Asked Questions

Can I use beef broth instead of water?

Yes! Beef broth or beef stock will add even more depth of flavor. Chicken broth also works in a pinch.

Do I have to caramelize the onions for the full 20 minutes?

For the best French onion soups, yes. That slow cooking is what gives the soup its rich flavor and deep golden brown color.

What cheese works best on top?

Mozzarella melts beautifully, but Gruyère cheese or Swiss cheese are more traditional options.