French onion soup is a classic delicacy that’s easy to make at home! You’re going to love breaking through the top layer of crusty bread and melted Gruyère, as flavorful caramelized onions are waiting just below.
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French onion soup demands your attention. It’s like making risotto, where you need constant watching and stirring to develop just the right texture and flavor. But that’s the only challenging part. When done right, the onions will melt effortlessly, and once you practice the caramelization technique a few times, this soup is a breeze to create.
The most eye-catching part of this dish is the crunchy toast on top. It gets covered with a blistery layer of cheese that completely blankets the surface. The bread gradually soaks up the rich broth with hints of wine and herbs. You’ll find delicious pieces of caramelized onions waiting for you at the bowl’s bottom below that.
Yellow onions provide a balance of sweet, spicy, savory, and mild flavor. Cut them into thinly sliced pieces, about ¼-inch thick. This size leaves some texture in the soup while giving more surface area for browning and becoming incredibly tender, to the point where it dissolves in your mouth.
Caramelizing the onions
Salting the onions at the beginning of cooking promotes quicker browning, good seasoning, and tender texture. I also add a small amount of brown sugar to help to accelerate the caramelization process. Cook them in melted butter and olive oil to add some richness to the vegetables. I use high-heat to kick-start browning, then reduce to medium for gentle cooking.
Gradual cooking and moving the onions in the pan draw the moisture and natural sugars to the surface, unlocking deep new flavors. Extended sauté time and reduced heat creates a more complex, sweet onion taste. The caramelizing process establishes the base of the entire soup and takes just over 20 minutes. I saute some minced garlic right at the end of cooking to add a pop of zing.
The flavorful soup base
A French Bordeaux, Beaujolais, or cabernet sauvignon works well for their balanced fruity, tannic, and acidic flavors. Deglaze the pan with the wine to infuse tasty bits of caramelized onion into the liquid. Make sure that the wine boils until it becomes au sec, or nearly dry.
The cooking duration ensures that most of the alcohol evaporates, and the flavors concentrate without tasting overly boozy. Next, add beef stock and aromatics like fresh thyme and a bay leaf to the pan. The soup simmers over low heat to coax all of the ingredients together, and further soften the onions. This process takes about 30 minutes.
Making the toast
You can use any crusty bread like a French loaf or baguette slices. I cut them into ½-inch pieces so that they create a thick crust on top of the soup. Plus, a thicker piece prevents them from getting too soggy when broiling the cheese. Toasting the bread before adding it to the soup keeps the surface crisper while adding a nice crunch.
Use gruyère cheese
Use a high-melting cheese like gruyère for optimal spread when broiled. It creates an irresistible gooey crust. This cheese originates from Switzerland and has a firm texture, nutty flavor, slight sweetness, and faint aged aroma. It grates easily and has a smooth and cohesive melt when heated, giving that sought-out cheese pull.
I look for a cheese aged from 4 to 6 months, so it’s not too dry. When broiled on a toasted piece of baguette and laid on the onion soup, the contrast of flavors and textures becomes irresistible. Provolone, gouda, or swiss cheese are suitable substitutes.
Broiling the cheesy toast
Portion out the soup into either four 12-ounce bowls or two 24-ounce bowls. Make sure that they are oven-safe, as the broiling temperatures are very intense. Lay one to two pieces of toasted bread slices on top of the soup then evenly sprinkle on the cheese.
Place the bowls on a baking sheet and immediately brown them until the cheese melts and turns light brown. I grab my spoon the second it’s ready to make sure I get a big scoop of crunchy cheesy bread before it becomes soggy.
What to serve this with
The sweetness of onions
My preference is yellow onions. They have the right balance of onion taste, slight sweetness, and savory notes. They release a natural sweetness as they cook, so there’s no need to use sweet onions such as Maui and Vidalia, which are high in sugar.
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French Onion Soup
- 2 pounds yellow onion, peeled, halved, cut into ¼-inch thick slices
- 1 tablespoon unsalted butter
- 1 tablespoon olive oil
- 1 teaspoon brown sugar
- ½ teaspoon kosher salt
- 1 tablespoon minced garlic
- 1 cup red wine
- 1 quart unsalted beef stock
- 3 sprigs thyme, plus more for garnish
- 1 bay leaf
- black pepper, as needed for seasoning
- 8 slices crusty bread or baguette, ½-inch thick slices
- 1 cup shredded gruyere cheese
- Heat a large pot or dutch oven over high heat. Melt the butter, then add olive oil, brown sugar, and salt, stir to combine.
- Add in the onions and stir to coat, saute, and frequently stir until onions begin to soften and lightly brown, about 5 minutes. Reduce heat to medium, cook onions, frequently stirring, until evenly browned, about 20 to 25 minutes.
- Once the onions finish caramelizing, add the garlic and saute until fragrant, about 30 seconds. Add the wine to deglaze the pan, stir to scrape any browned bits on the bottom. Increase heat to high, allow the wine to boil and evaporate, frequently stirring, about 4 to 5 minutes.
- Add the beef stock, thyme sprigs, and bay leaf. Bring stock to a boil, cover, and reduce to a simmer over low heat, about 30 minutes.
- Discard thyme sprigs and bay leaf. Season the soup with salt and pepper to taste.
- Place the sliced bread on a baking pan in the center of the oven. Broil on until golden brown, about 3 to 5 minutes per side.
- Add soup to four 12-ounce bowls, top with toasted bread slices (1 to 2), and evenly distribute the cheese on top of each piece. Alternatively, you can use two larger 24-ounce bowls for more significant portions. Place the bowls on top of a sheet pan.
- Broil on high, about 8 inches away from the oven’s top until the cheese melts and turns golden brown, about 5 to 6 minutes. Garnish the soup with black pepper and chopped thyme. Serve immediately while still hot and bread is crunchy.
- Soup base can be made ahead of time or frozen and reheated before serving.
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