French Onion Soup

French onion soup takes the humble onion and makes it the star of the show. Between its deeply caramelized onions and bubbly cheese toast lid, it’s the meal of our dreams.

If you’ve only eaten French onion soup in restaurants, you’ll be surprised by how easy it is to make at home. With just a bit of time and attention, you too can transform a handful of basic pantry ingredients — onions, broth, butter, and cheese — into a luxurious bowl of silky, melty onions swimming in a rich broth. 

In this recipe, I’ll give you the lowdown on the best type of onions to use, which wine to avoid, and how to select the perfect cheese. Before you know it, you’ll be impressing your friends and family with this delicious bistro classic.

• Onions: Yellow onions have the right balance of sharpness and sweetness, which makes them the best choice. 
• Broth: Soup is always a great place to use homemade stock. But store-bought is really OK. Opt for a low-sodium broth so you can control the salt level as the soup reduces, and balance it with the salty Gruyère on top. Beef broth is traditional for the rich color and flavor it brings to the soup.
• Wine: There was an interesting split in the recipes I researched that used white or red wine. In addition to deglazing and dislodging any stuck bits on the bottom of the pot, the acidity and flavor of the wine cuts through the natural sweetness of the onions and introduces some other flavor notes for dimension in the broth. I chose white wine because it is overall less tannic and intense than red wine, making it a complementary flavor to the onions rather than a dominating one. Choose a dry white wine, but avoid ones that are overly buttery, oaky, or tropical.
• Cheese: Gruyère is sharp, salty, and melty, which is the perfect trio for the flavors in the broth. Sprinkling a little into the soup before topping gives the broth a kiss of cheesy flavor.
• Bread: Sliced bread is the raft that floats on top and carries the bubbly cheese topping. French baguette has the right mix of gentle, crusty edges and a soft interior, and it is the correct length to nestle on top of a crock. There is no need to pre-toast the bread. You want the bottom to soak up some of the juices so you can break through with a spoon. 

If caramelizing onions gives you trouble, take heart that the onions in this recipe do not need to be cooked quite as dark as that. It’s easier to control the browning in a pot with a thick, heavy bottom, which is why a Dutch oven (we have an opinion on which one is best!) is ideal. If using a pot made out of a thinner material, keep an eye on the temperature under the pot to avoid scorching.

1. Slice your onions. Halve and slice onions from root to tip for slightly shorter strips that are easier to slurp up and won’t become a big tangle. Do not shave them paper thin. Instead, cut them about 1/4-inch thick. Too thin, and the onions will end up mushy or start breaking apart. Despite the long cooking time, they will still have a little texture if you start with a slightly thicker slice from the start.
2. Caramelize the onions slowly in butter, stirring for even browning. Starting the onions covered helps them steam and collapse quickly, giving the cooking a head start and making it easier to stir the initially large volume of onions. Stirring frequently once the onions start to brown and scraping the bottom of the pot helps the onions brown slowly and uniformly, as well as avoiding burning or tasting bitter. If one side of the pot gets dark, rotate the pot on the burner so that the hot spot doesn’t stay in one area.
3. Add the broth and let simmer. The goal here is to concentrate the stock. The pale liquid will darken and thicken just enough that the onions are suspended in the broth rather than feeling like two separate ingredients. 
4. Make the cheese toasts. Divide the soup between bowls, top with cheese, bread, then more cheese. Broil until the cheese is melted and bubbling, and any bread edges are toasted. 

If this is a soup you enjoy, consider getting some onion soup crocks. They are not expensive, make the soup feel extra special, and have plenty of other uses.

• Use chicken or veggie broth. Although beef broth is traditional, you can substitute homemade chicken broth or vegetable broth. You can even consider replacing some with mushroom broth, as it is full of umami flavor and will deepen the final color. 
• Any Gruyère will work. You may encounter Gruyère at the store that has been aged for different lengths of time. A younger cheese will be creamier and less sharp, while a more aged block of cheese will be drier and bolder in flavor. Either option works, depending on your preference. 
• Cube the bread. Try cubing the bread instead for ease of eating. As long as the top of the soup is well covered with bread to hold all the cheese, it works.

French onion soup can be served as a first course or as the main dish with a few sides. Here are some great options.

• A green salad with a sharp vinaigrette to help cut the soup’s richness.
• A plate of hot crispy french fries to bring home that bistro vibe.