Classic French Onion Soup

Classic French onion soup, or Soupe A L’Oignon Gratinee, is hearty, comforting, and incredibly delicious. Rich beef stock is kissed with vermouth and brandy then simmered with caramelized onions. Crisp, garlic-infused croutons and melted Gruyere cheese go on top.

Where Does This Soup Recipe Come From?

This is Julia Child’s French onion soup recipe from Julia Child’s The Way to Cook. One of my favorite go-to cookbooks, it’s filled with traditional French dishes with clear instructions. Mastering the Art of French Cooking is another great cookbook for any lover of French cuisine.

Although French onion soup sounds fancy, it is really a simple soup. With minimal ingredients, the hardest part is waiting for the onions to caramelize.

Unlike some recipes I’ve seen for French onion soup, this one does not contain Worcestershire sauce or soy sauce. I’m not sure how this became a thing. Worcestershire sauce is a British condiment and soy sauce is Asian. There is no need to add them to a recipe for classic French onion soup!

What Kind of Cheese is Best for French Onion Soup?

Traditionally, Swiss Gruyere cheese is used. If you have trouble finding gruyere, substitute Swiss cheese. You can either slice it or shred it. I’ve found Trader Joe’s Swiss & Gruyere shredded blend works well for classic French onion soup recipes, and won’t break the bank.

Should I Use Wine or Brandy In the Soup?

A dry white or red wine is often used in French onion soup recipes, but for this, I use Vermouth and brandy.

Vermouth is a fortified wine and is great to have on hand for cooking. It’s perfect for deglazing a pan to make a quick sauce, and it keeps well in the cupboard, which means you don’t have to open a bottle of wine every time you need it for a recipe.

If you prefer to omit the alcohol, you can make this onion soup without wine and brandy, but the alcohol does burn off during the time the soup is cooking.

What Kind of Onions Do You Use In French Onion Soup?

Sticking with the classic French onion soup recipe, yellow onions are the best. Yellow onions lend themselves to a long slow cooking like stews or soups. Red onions are best raw or quickly pickled. 

This recipe calls for 2 1/2 pounds of sliced yellow onions. There are lots of ways to prepare them before you caramelize!

You can cut them by hand, or use a mandoline or food processor, and slice them nice and thin in about 5 minutes. This mandoline works perfectly and also can be used to make great French fries.

How Do You Caramelize Onions?

Caramelized onions are delicious and can be used in many ways! Sometimes, I’ll make extra to have for this Brie and Fig Jam appetizer with caramelized onions, but they can also be used as pizza toppings, on burgers, or as an addition to sandwiches and salads.

Caramelizing onions transforms them from sharp and crunchy to sweet and golden brown. The key is to let them cook slowly.

After peeling and slicing your yellow onions, you’ll heat a pan to medium heat, add some unsalted butter or olive oil (or both for extra flavor!), then add the onions.

At first, there will be a lot of liquid, but as it evaporates, the onions will start to cling to the bottom of the pot and turn a lovely golden brown.

Stir them occasionally, reducing the heat to medium-low. Adding just a 1/2 teaspoon of sugar or a sprinkle of salt helps the caramelization process.

How To Thicken French Onion Soup

French onion soup is thickened with a small amount of flour, just 2 Tablespoons. You definitely want a thin, brothy soup, so it’s just enough flour to give it some body.

Can You Make Gluten-Free French Onion Soup?

You can absolutely make a gluten free French onion soup!! I’ve made it gluten-free in a couple of ways.

You can substitute flour with a gluten free all-purpose flour blend, or if you’re grain-free, skip the flour and croutons altogether. It may result in a thinner broth, but that’s fine for this soup. You can also add additional cheese to the finished soup. One thing to note about the cheese is it will usually sink to the bottom without the croutons or bread.

What Is a Gratinee?

The term “gratinée” comes from the French verb “gratiner,” meaning to broil or to crust over.

A French onion soup gratinée is where Gruyere cheese and a slice of baguette bread are browned under a broiler. This melts the cheese and forms the famous browned crust over the top of the soup.

How Do You Make French Onion Soup?

Start by slicing the onions thinly. Using a mandoline or food processor makes this task go quickly. But I can’t help with the tears!

Heat the butter and olive oil over medium heat. Heating both these fats together prevents the butter from burning. Add all the sliced onions. It’ll seem like a lot of onions, but just like spinach, they cook way down!

The onions need to cook for a while. First, the liquid will evaporate, then they’ll start to brown. Add the sugar and salt at this step. Stir them every once in a while. You’ll want to brown them, not burn them.

Once the onions are a deep golden brown, add the flour and cook for a couple of minutes.

Add 2 cups of hot stock. The stock or broth should be hot to help incorporate the flour. Once you’ve added and blended the 2 cups of stock, add the remaining stock, vermouth, and brandy, along with a sprig of fresh thyme.

Loosely cover the pot and reduce the heat to low, simmering and cooking slowly for about 1 1/2 hours. If the soup reduces too quickly or by too much, add more broth.

Check the seasoning. As the soup reduces, the flavor intensifies. Season to taste with black pepper and kosher salt if needed.

Preheat the broiler, and slice the baguette on the diagonal into 3/4″ slices. Naturally, a good French baguette is best! If you prefer to have French onion soup croutons to a full slice of bread, then feel free to slice the bread into crouton-size squares!

You can serve the rest of the loaf on the side or with another soup! For the nutritional value, I’ve only included half of a baguette since you’ll only need a slice or two for each bowl.

Brush each side of the baguette with olive oil, then rub each side with the cut end of a clove of garlic. Toast the bread until golden brown on each side.

Pour the soup into bowls, and place them on a cookie sheet. Cover each bowl with one or two slices of toasted bread and then a handful of grated Gruyere cheese.

Place the cookie sheet under the broiler. Keep an eye on it. The cheese will melt quickly!

Be careful when serving as the soup bowls will be very hot!

What’s the Best Bowl to Use For French Onion Soup?

You’ll need oven-proof bowls able to withstand a broiler. I’ve found this super cute cocotte set with little lids. They’re also perfect for individual chicken pot pies.