Soupe à l’oignon: the secret to creamy onions that melt in your mouth
Soupe à l’oignon is much more than a simple soup; it is the warm embrace of French cooking on the coldest days.
However, a common issue many face when reproducing it at home is the texture of the onions: if they are not cooked correctly you risk a watery broth with pieces that still taste “raw” or, conversely, burned onions that leave an unpleasant bitter aftertaste.
To solve this problem, the secret lies in patience and the correct use of flour, which transforms the broth into a silky cream.
In this version, inherited from a dear French friend of my mother, I will show you how the combination of oil and butter allows the onions to stew without burning, keeping an incredible delicacy.
The final touch, gratinating in individual cocottes with toasted baguette and Emmental, creates that contrast between the crunchy crust and the gooey center that is the true signature of this dish.
Whether you serve it for a romantic dinner or as a winter comfort, this soup will win over even those who usually avoid onions. Prepare your cocottes: we are about to bring a corner of Paris directly to your table.
Gratinated onion soup: the Parisian recipe with a Gruyère crust
- Difficulty: Easy
- Cost: Inexpensive
- Preparation time: 30 Minutes
- Cooking time: 50 Minutes
- Portions: 4
- Cuisine: French
- Energy 506.26 (Kcal)
- Carbohydrates 52.74 (g) of which sugars 11.30 (g)
- Proteins 16.30 (g)
- Fat 26.72 (g) of which saturated 8.18 (g)of which unsaturated 4.36 (g)
- Fibers 4.11 (g)
- Sodium 1,645.38 (mg)
Indicative values for a portion of 200 g processed in an automated way starting from the nutritional information available on the CREA* and FoodData Central** databases. It is not food and / or nutritional advice.
* CREATES Food and Nutrition Research Center: https://www.crea.gov.it/alimenti-e-nutrizione https://www.alimentinutrizione.it ** U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2019. https://fdc.nal.usda.gov
Ingredients for French Onion Soup
- 1 1/3 lb white onions
- 4 1/4 cups vegetable broth
- 1.8 oz all-purpose flour
- 2 tbsp extra-virgin olive oil
- 3 1/2 tbsp butter
- to taste salt
- 1 pinch black pepper (freshly ground)
- 3.5 oz Emmental
- 8 slices baguette (toasted)
Gratinated onion soup: the Parisian recipe with a Gruyère crust
Start by cleaning the onions: peel them and slice them thinly so that they cook evenly. In a large pot (preferably cast iron), heat the oil with the butter. When the butter foams, add the onions and let them soften over medium heat for about 5–10 minutes. Once they become translucent, dust them with the flour and stir well until you see the bottom starting to color.
Add the hot vegetable broth a little at a time, continuing to stir to avoid lumps. Lower the heat to the minimum and let cook for about 35–40 minutes without a lid. The onions should almost fall apart, turning the broth into a thick, fragrant cream. At the end of cooking, adjust salt and pepper.
Toast the baguette slices in the oven for a few minutes until crisp. Divide the hot soup into individual cocottes, place two slices of bread on each and generously cover with grated Emmental. Place under the broiler at 482°F for about 10 minutes: the crust should turn golden and piping hot. Let rest for two minutes before serving so you don’t burn yourself!
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📝 Notes on Ingredients and Substitutions
Onions: White onions are milder, but yellow onions caramelize better thanks to their higher sugar content.
The Cheese: Emmental is great for gratinating, but for an authentic French flavor look for Gruyère PDO or Comté.
The Bread: Baguette is the classic choice, but a slice of rye bread can give an interesting rustic note.
📦 Storage
Onion soup (without bread) keeps in the fridge for 2–3 days. I recommend gratinating it only at the moment of consumption to avoid the bread becoming too soggy.
🔄 Alternatives and Variations
Italian-style Soupe: You can deglaze the onions with half a glass of dry white wine before adding the broth for a boost of acidity.
Richer Version: Add a sprig of thyme or a bay leaf during cooking for a more woodland aroma.
💡 Tea’s Tips
If you want a darker brown color (typical of Parisian brasseries), let the onions “stick” slightly to the bottom of the pot before adding the broth, then deglaze with a ladle of liquid scraping the bottom well: that little “charred” note is pure flavor!
FAQ (Questions and Answers)
1. Can I use meat broth?
Absolutely yes! The traditional French recipe would use beef broth, which gives a darker color and a much more robust flavor.
2. The onions are still a bit crunchy, what did I do wrong?
Probably the heat was too high. Onions need a gentle, long cooking time to lose their fiber and become creamy.
3. Can I prepare it in advance?
Yes, the soup is even better the next day. Reheat it well on the stove and proceed to gratinate at the last minute.
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