French Onion Soup

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.

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.

Onion selection

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

• Beef Bourguignon
• Salmon en Papillote
• Steamed Mussels