How to cook a good homemade French onion soup

Nothing is more comforting than a good onion soup au gratin after a day of skiing or snowball fighting—and it’s easy to cook, too. You probably already have everything you need to prepare it at home and, thanks to the following tips, you won’t even need a recipe to make a successful soup.

A soup that’s adaptable

Onion soup can be gourmet and refined, or can be a fridge-cleaning-type of meal, depending on your taste and budget. It is made with onions, broth, bread and cheese—all basic, accessible ingredients. You just need to know the right techniques to adapt it to your liking.

What you need to know about onions

onions

The basis of your soup lies in this ingredient. Here’s how to give it prominence.

Varieties

Traditionally, yellow onions are used to make onion soups, but almost any variety can be part of its ingredients. Vidalia onions, for example, are sweeter and will lend that taste to the soup. You could also mix several varieties that will balance milder and more prominent flavours.

Cooking

To get that sweet onion flavouring, they must be caramelized gently and slowly in a saucepan. Add butter or oil and coat the minced onions well. Cook them over low heat for about 20 minutes until golden brown. But be careful: They must not brown too much or they will risk giving a bitter taste to the soup.

Quantity

About 6 medium-sized onions and 2 litres of broth make a soup for 4 servings, but you can adjust according to the consistency you want in your soup and the size of the onions.

Pro tip for watery eyes

We can’t guarantee that you won’t shed a tear or two while cutting that massive amount of onions (unless you wear swimming goggles), but if your knife is sharp, it will crush the vegetable less, thus less of the enzymes that make eyes water will be released.

Liquids that give the soup taste

To deglaze onions and to make the most of your broth, you can use what you have on hand. Here are some suggestions.

To deglaze

Before pouring broth or alcohol to deglaze onions, coat them with a little white flour or toasted flour (about 1 to 2 tablespoons), which will allow the broth to thicken. Then deglaze the onions by adding a small amount of liquid, such as:

White or red wine
Lager for a light-tasting broth or dark beer for a malty taste
Beef, chicken or vegetable broth
Liqueurs (brandy, cognac, etc.)

For the broth

Use the broth of your choice (chicken, beef, vegetable) to cover the onions well and simmer over medium heat, about 20 minutes, or until your soup reaches the desired consistency.

The finishing touch: croutons au gratin

An onion soup would not be as gourmet without the slice of bread au gratin that is placed on top. Here are some options.

Bread

Choose a bread that has a fairly crispy crust (baguette, Belgian, sourdough, walnut, etc.). A sliced sandwich bread could get soggy too quickly. Before placing the slices of bread on the soup, brush them with oil and place them in the oven for a few minutes.

Cheese

The classic onion soup is made with Gruyère cheese, but any cured firm or semi-firm cheese will do, such as a cheddar or Tomme. Just opt for a cheese that melts well.

The crust

Make sure the slice of bread covers the surface of the bowl of soup. You can add the gratin to the crouton separately in the oven and then place it on the soup, or use heat-proof bowls and add the gratin to the crouton in the soup.