Authentic French Onion Soup (Soupe à l’Oignon Gratinée)

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Table of contents:

• How to Make Authentic French Onion Soup
  • Ingredients
  • Equipment
  • Instructions
• Tips for TRUE French Flavor 🇫🇷
• Origins of French Onion Soup (Soupe à l’Oignon Gratinée)
• Best Wine Pairings for French Onion Soup
• Cooking Notes:
• More Mediterranean Comfort Food Recipes
• FAQs – French Onion Soup
• Nutrition Facts (Per Serving)

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How to Make Authentic French Onion Soup

Ingredients

For the onion soup

• 4–5 large yellow onions (about 1 kg), thinly sliced
• 3 tbsp unsalted butter
• 1–2 tbsp Extra Virgin Olive Oil 
• 2 cloves garlic, minced
• 1 tbsp flour (optional but traditional for thickening)
• 150 ml (⅔ cup) dry white wine OR dry French vermouth
• 1 liter (4 cups) high-quality beef stock (traditional)
• 1 bay leaf
• 2–3 thyme sprigs
• Salt and black pepper, to taste

For the gratinéed topping

• ½ French baguette, sliced into thick rounds
• 200 g (2 cups) grated Gruyère (traditional) – Comté or Emmental also work
• Optional: a touch of Parmesan for extra browning
  

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Equipment

• Heavy-bottomed pot or Dutch Oven
• Wooden spatula
• Chef Knife
• Wooden Cutting Board
• French Onion Soup Bowls 
• Baking Tray
• Parchment paper
• Box Grater
• Ladle
• Broiler or Oven with grill function

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Instructions

Step 1 – Caramelize the onions (the most important step!)

• Heat butter and olive oil in a heavy pot (like a Dutch oven).
• Add the sliced onions and a pinch of salt.
• Cook on medium-low for 45 minutes to 1 hour, stirring every 15-20 minutes.
• Onions should become a deep golden brown color and will be very soft and jammy.
  

Note 👉 Slow caramelization is the key to authentic French flavor.

Step 2 – Build the soup

• Once onions are caramelized, add garlic and cook 1 minute.
• Stir in the flour and cook another minute (optional step to slightly thicken).
• Deglaze with the white wine, scraping up all browned bits.
• Add the beef stock, bay leaf, thyme, salt, and pepper.
• Simmer uncovered for 20–25 minutes.
• Taste and adjust seasoning.

Step 3 – Prepare the toasted bread

• Toast baguette slices in the oven until crisp (2-3 minutes under the grill/broiler).
• For extra authenticity, rub lightly with a cut garlic clove.
  

Step 4 – Assemble and broil

• Ladle hot soup into oven-safe bowls.
• Float 2–3 toasted baguette slices on top.
• Cover generously with Gruyère.
• Place bowls under a hot broiler for 2-3 minutes until the cheese melts and starts to bubble and become golden. A little browning around the edges is also good for flavor!

Serve

Serve piping hot — the cheese crust should be gooey, melty, and slightly crisp in spots.

Tips for TRUE French Flavor 🇫🇷

• Use yellow onions, not sweet onions.
• Avoid shortcuts — authentic soup depends on slow caramelization.
• Beef stock is traditional, though half-and-half (Beef/chicken) stock adds balance.
• Gruyère is essential, giving the classic nutty, stringy melt.
• Use dry wine only — sweet wine will throw the flavor off.

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Origins of French Onion Soup (Soupe à l’Oignon Gratinée)

Onions have been used in soups since ancient times because they were cheap, abundant, and easy to store. Versions existed in Roman times, but the dish as we know it today is unmistakably French.

The caramelized-onion, beef-stock–based version became popular in the 17th and 18th centuries, especially in particular regions of Paris:

⭐ In the Les Halles Market District (Paris)

• The massive wholesale market in central Paris fed the entire city.
• Workers, porters, bakers, and fishmongers began their days before dawn.
• French onion soup was a cheap, warming, restorative broth served in nearby taverns.
• It became known as a kind of hangover cure for partiers finishing long nights in Paris.

This association made it a staple of bouillons (casual worker cafés), and later, bistros.

Originally, it was simply a hearty onion-and-stock soup.
The famous gratinée version — topped with toasted bread and melted cheese — became widespread in the 19th century, when:

• French cafés and brasseries added broilers/salamanders to their kitchens
• Gruyère cheese became popular and widely available
• The soup transitioned from “workers’ breakfast” to a classic Parisian comfort dish

This version is the one now served in bistros worldwide.

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Best Wine Pairings for French Onion Soup

🇫🇷 White Burgundy (Chardonnay) — The Classic Pairing

A lightly oaked or unoaked Bourgogne Blanc or Mâcon-Villages is considered the perfect companion.

Why it works:

• High acidity cuts through cheese
• Slight nuttiness echoes the melted Gruyère
• Complements, rather than competes with, the caramelized onion sweetness

Examples:

• Mâcon-Villages
• Saint-Véran
• Chablis (unoaked, crisp, excellent match)

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🇫🇷 Alsace Pinot Gris or Pinot Blanc

Alsace whites are aromatic but not overwhelming — excellent with onion-heavy dishes.

Why it works:

• Subtle fruit + minerality
• Clean, long finish
• Gentle structure for a rich soup
  

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🇫🇷 Dry Chenin Blanc (Loire Valley)

A Savennières or Vouvray Sec handles richness exceptionally well.

Why it works:

• Naturally high acidity
• Herbal and mineral notes pair beautifully with broth and onions
  

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🍷 Red Wine Pairings (for red-wine lovers)

While white wine is more traditional with onion soup, some reds pair surprisingly well — as long as they are light-bodied and low in tannins.

🇫🇷 Beaujolais (Gamay)

The best red with French Onion Soup.

Why it works:

• Bright acidity
• Red fruit and slight earthiness
• No heavy tannins to fight the sweetness of onions

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🇫🇷 Pinot Noir (Burgundy or Oregon)

Silky and subtle enough not to overwhelm the dish.

Why it works:

• Elegant acidity lifts the cheese topping
• Earthy undertones complement onions

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Cooking Notes:

Wine or Vermouth? 

In classic Parisian bistros, dry white wine is far more common than dry French vermouth in traditional French Onion Soup. But that’s not to say wither are wrong. We suggest try making with both and see which version you prefer. 

Most Popular in Parisian Bistros:

→ Dry white wine (usually a dry French wine such as Chardonnay, Sauvignon Blanc, or a neutral table wine).

Why white wine is more commonly used

• It has been the standard deglazing liquid for French onion soup in bistro kitchens for decades.
• Bistros typically cook large batches, and inexpensive dry white wine is always on hand.
• It adds acidity and brightness without changing the traditional flavor profile.
• It’s what you’ll find in most Paris restaurant kitchens today.

What about dry vermouth?

Dry French vermouth (like Noilly Prat) is used in some modern or chef-driven versions, especially when cooks want:

• A stronger herbal aroma
• A slightly more complex, refined flavor

But it is not the traditional or most common choice.

• 150 ml (⅔ cup) dry white wine OR dry French vermouth

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Nutrition Facts (Per Serving)

Nutrient	Amount per Serving	% Daily Value (DV)
Calories	~425 kcal	21%
Total Fat	22 g	28%
Saturated Fat	13 g	65%
Trans Fat	0 g	—
Cholesterol	60 mg	20%
Sodium	1160 mg	50%
Total Carbohydrates	34 g	12%
Dietary Fiber	3 g	11%
Total Sugars	10 g	—
Added Sugars	0 g	0%
Protein	19 g	38%
Vitamin D	0.2 mcg	1%
Calcium	430 mg	33%
Iron	1.4 mg	8%
Potassium	430 mg	9%
Vitamin A	~700 IU	14%
Vitamin C	~9 mg	10%

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⭐ Notes on These Values

• Beef stock is responsible for a large portion of the sodium (can vary widely by brand).
• The cheese contributes most of the saturated fat, calcium, protein, and calories.
• The baguette adds carbohydrates and some of the sodium.
• Onions contribute natural sugars and some potassium.

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FAQs – French Onion Soup

1. Can I use sweet onions instead of yellow onions?
Yellow onions are strongly recommended for authentic French Onion Soup because they develop deep, savory-sweet flavor during long caramelization. Sweet onions can make the soup overly sweet and less balanced.

2. Do I have to caramelize the onions for a full hour?
Yes — slow, deep caramelization is the foundation of classic French flavor. Rushing this step results in a flatter, less complex soup.

3. Can I make this soup vegetarian?
Yes. Use a rich vegetable stock or a mix of vegetable + mushroom broth. The flavor will be lighter and less traditional but still delicious.

4. What can I use instead of Gruyère?
Comté, Emmental, or a blend of Gruyère + Parmesan work well. Avoid pre-shredded cheese—it won’t melt or brown as nicely.

5. Can I make the soup ahead of time?
Absolutely. The soup (without bread and cheese) stores very well for up to 3–4 days in the fridge and freezes for up to 3 months. Assemble and broil just before serving.

6. Can I skip the wine?
Yes. Replace it with more stock plus 1–2 tsp of white wine vinegar or lemon juice. The acidity helps balance the sweetness of onions.

7. Why add flour?
Flour is a traditional bistro technique used to give the broth slight body. It’s optional—you can leave it out for a thinner, more rustic soup.

8. What type of bowls should I use for broiling?
Oven-safe ceramic or stoneware soup bowls are ideal. Never use glass bowls unless they are explicitly broiler-safe.

9. What’s the best bread for the topping?
A firm French baguette works best because it holds up under the cheese without turning mushy.

10. How do I keep the bread from getting too soggy?
Toast the baguette slices until crisp and dry. This helps them hold texture once submerged in the soup.

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