I’ve been craving for one of my favorite soups for days now: a good French Onion Soup with a cheesy toast on top.

This so called soupe à l’oignon gratinée is a great recipe for a starter or a light dinner on cold winter days. 

• The origin of the French onion soup
• What is a French onion soup ?
• List of ingredients
• How to prepare a French onion soup ?
• Géraldine’s tips 
• Frequently Asked Questions

The origin of the French onion soup

As its name suggests, a French onion soup or soupe à l’oignon is a classic French soup recipe.

Before it became so popular, it was this onion soup was a dish of the poor people. Onions were easy to grow and the bread on top was actually old bread.

What is a French onion soup?

The traditional French onion soup is a thick flavorful soup made with caramelized onions, chicken or beef stock and traditionally covered with a cheesy bread on top of the soup.

This soup is usually served as a starter in small individual casseroles but as it is relatively hearty soup, it can also be served as a main course with a green salad and a cheese plate for example. It is a treat!

List of ingredients

This recipe is really economical as you only need a few rather cheap ingredients.

You will find below my comments and substitute options regarding the main ingredients.

Onions: This onion soup is traditionally made with yellow onions. You can replace them with other varieties of onions such as red onions or sweet onions.

Broth: Since I wanted a vegetarian recipe, I used vegetable broth. You can also use beef stock or chicken stock instead. 

Butter: I used soft French butter with a minimum of 82% fat.

White wine: White wine is used to deglaze the onions and also to give the soup a touch of acidity. You can also use red wine. In this case, the soup will have a darker color. 

Cognac: This is an optional ingredient, but I did add a dash of cognac to the onion soup with the white wine. It gives a delicious woody note to the soup. 

Flour: Flour is used to thicken the soup slightly. I use all-purpose flour. You can replace it with cornstarch or potato starch. In this case, halve the quantity because cornstarch has twice the thickening power. 

Nutmeg: Nutmeg adds a delicious flavour to the soup. 

Bread: Traditionally, slices of stale baguette are used and will soften in the soup. Of course, you can also use fresh bread. In this case, I recommend toasting it beforehand so that it holds together better. 

Garlic: You need a clove of garlic to rub on the bread and give it a nice garlic taste. 

Grated cheese: Grated cheese is the gourmet touch in this recipe! I use grated gruyere cheese but you can use other cheeses like grated Comté, Gouda or Emmental.

You will find the exact quantities in the recipe card.

How to prepare a French onion soup?

ONIONS: First, peel the onions and cut them in half and then into slices.

In a large pot or dutch oven, sauté the onions with a drizzle of olive oil over medium-high heat. After they start to become translucide, add the butter and sauté for another 10 minutes until golden brown.

DEGLAZE: Deglaze with the white wine and cognac and stir with a wooden spoon to loosen the brown bits that have clung to the bottom of the pot. Let reduce for 2 minutes. 

SIMMER: Add the flour and mix well. Pour in the vegetable broth and season with pepper and nutmeg. Simmer on medium heat for 30 minutes. 

BAKE: Cut the slices of baguette and toast them. Count one or two slices per serving. Rub the toasted baguette slices with a fresh garlic clove. 

Place your mini casseroles or oven-proof bowls or ramekins on a baking sheet covered with parchment paper. Pour a ladle of soup into each mini casserole.

Place one or two slices of baguette on top. Top with grated cheese. Broil in the oven for 3-5 minutes. 

Serve while still warm. 

Géraldine’s tips 

• Decorate the onion soup with fresh thyme sprigs, not only is it very pretty but the thyme gives a great taste to the soup. 
• To give this soup a deeper flavor, you can add a drizzle of balsamic vinegar or soy sauce at the end of the cooking.

More soup recipes

• Finnish Salmon Soup (Lohikeitto)
• Creamy Veggie Tortellini Soup
• Broccoli, Pea and Ginger Soup
• Creamy Cauliflower Soup (Low Carb)

 Frequently asked questions 

Can I make this onion soup in advance?

Yes, absolutely! You can prepare the onion soup up to 48 hours in advance. Divide it into individual containers at the last minute and broil with the bread and cheese it just before serving. 

Can I freeze this onion soup? 

Yes, you can. Place the onion soup, without the bread and cheese, in an airtight container. It will keep for up to one year in the freezer.

Can I make a vegan version? And gluten-free?

Yes, absolutely. For a vegan version replace the butter with olive oil or vegetable butter and the grated cheese with a vegetable version as well. 

For a gluten free version, you only have to replace the flour by half the amount of cornstarch and the bread by gluten free bread.

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