Which onions are best for French onion soup?

French onion soup is a delicious and hearty soup that is popular in both France and around the world. It features a rich, deeply-flavored broth and is topped with slices of toasted bread and melted cheese. The key to making great French onion soup lies in slowly caramelizing onions to develop their natural sweetness and depth of flavor. But which type of onion works best?

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Onion Varieties for French Onion Soup

There are several varieties of onion that can be used to make classic French onion soup:

Yellow Onions – These are the most commonly used onions for French onion soup. Yellow onions have a balanced, mildly sweet flavor that caramelizes well.
White Onions – White onions are sweeter and more delicate in flavor than yellow onions. They work very well caramelized in French onion soup.
Red Onions – Red onions add a pop of color and a slightly tangy, sweet flavor. They are excellent for French onion soup.

Shallots – Shallots have a gentle, subtly sweet onion flavor. They caramelize beautifully and are a popular choice for onion soup.
Sweet Onions – Sweet onion varieties like Vidalia and Walla Walla can also be used. They have a very sweet, mellow taste when caramelized.

While most any type of onion can be used, most chefs recommend using a mix of different varieties. Combining sweet, tangy, and rich-flavored onions creates the most complex, balanced flavor.

How to Choose Onions for French Onion Soup

Here are some tips for selecting the best onions to use:

Go for firm, dense onions. Onions that feel lightweight often have higher water content. Denser onions caramelize better.
Avoid onions with soft spots, sprouts, or mold. Damaged onions won’t hold their shape during long cooking.

Medium to large-sized onions work best, as they’re easier to slice into uniform pieces.
Store onions in a cool, dry place until ready to use. Cut away any sprouted ends or damaged outer layers before cooking.

Preparing the Onions

Properly preparing the onions is vital for French onion soup. Here are some tips:

Peel and slice both ends off the onions first.
Slice the onions pole to pole into thin, uniform slices. Aim for about 1/4 inch thick.
A mandoline makes quick work of uniformly slicing onions.

Separating the onion slices into rings helps them soften faster during cooking.
Soak the sliced onions in cold water for 5-10 minutes to remove some of their harsh, raw flavor.

Cooking the Onions

Cooking the onions slowly is the secret to maximizing their flavor. Here’s how:

Cook the onions in a soup pot or dutch oven over medium-low heat.
Add a couple tablespoons of butter or olive oil to prevent sticking.
Cook slowly for 45-60 minutes, stirring frequently.

The onions will soften, then caramelize to a deep brown color.
Scrape the bottom of the pot often to prevent burning.
If the onions seem dry, add a splash of water or stock.

Add a pinch of sugar near the end to enhance browning and sweetness.

Taking the time to properly caramelize the onions is the foundation of French onion soup flavor.

Choosing the Broth

The onions are cooked in a savory broth that builds layers of flavor. Good broth choices include:

Beef broth – For traditional French onion soup flavor.
Chicken broth – Lends a lighter body and milder flavor.
Vegetable broth – Works for vegetarian/vegan versions.

White wine – Adds acidity and fruitiness when combined with broth.
Water – Can be used, but imparts little flavor on its own.

For best results, use a 50/50 combination of beef or chicken broth with a dry white wine, such as a Sauvignon Blanc or Pinot Grigio. The wine provides brightness to balance the rich broth.

Selecting the Bread

The soup is topped with a slice of toasted bread smothered in melted cheese. Look for bread that:

Is stale or baked very crisp. Soft bread disintegrates when broiled.
Has a dense crumb to stand up to broiling. Baguettes and rustic loaves work well.

Can be cut into 1/2 to 1 inch thick slices. Thin slices won’t hold toppings.
Has a light interior crumb, not whole grains. The melted cheese sinks in better.

Some good options are French baguettes, ciabatta, Italian bread, or a simple white loaf. Lightly toast or grill the slices first to help them hold up when broiled.

Choosing the Cheese

Opt for cheeses that melt smoothly for the best cheese topping. Great options include:

Gruyere – The classic choice, with a nutty, rich flavor.
Emmental – A Swiss cheese with melty, stretchy qualities.

Mozzarella – Melts beautifully into the bread.
Provolone – Sharp, tangy flavor.
Cheddar – Aged cheddar has potent flavor.

Use grated cheese so it melts quickly and evenly when broiled. Mixing Gruyere with Emmental, mozzarella, or cheddar creates a complex flavor.

Onion Soup Cooking Tips

Follow these tips when making the soup:

Cook a mix of onion varieties for the most flavor.

Add a pinch of salt and sugar when cooking onions.
Deglaze the bottom of the pot with a splash of wine or water to incorporate browned bits.
Simmer the broth for 30-45 minutes to develop flavor.

Taste and season with salt, pepper, and herbs if needed.
Ladle the broth into oven-safe bowls before adding the bread and cheese.
Broil until the cheese is bubbly and browned.

Taking the time to properly caramelize the onions and build the soup’s flavor makes all the difference!

Onion Soup Ingredients

Here is an overview of the ingredients needed to make classic French onion soup (serves 4):

Ingredient	Amount
Onions, sliced – mix of yellow, white, red	3-4 large onions
Butter or olive oil	2-3 Tbsp
Beef broth	4 cups
Dry white wine	1/2 cup
Fresh thyme	1 Tbsp chopped
Bay leaf	1
Salt and pepper	To taste
Bread, cut into 1 inch slices	4 slices
Grated cheese – Gruyere, Emmental, etc.	1/2 cup

These simple ingredients create the rich, flavorful French onion soup that people love!

Conclusion

French onion soup achieves its remarkable depth of flavor through the slow caramelization of onions. The best results come from cooking a mix of onion varieties, such as yellow, white, and red onions, with shallots or sweet onions also lending their own character. Slice the onions uniformly and soak them briefly to mellow their flavor. Then cook the onions for 45-60 minutes over low heat until deeply caramelized. When combining the cooked onions with a flavorful broth and wine, topped with toasted bread and melted cheese, you have the perfect French onion soup!