Classic French onion soup, or “Soupe A L’Oignon Gratinee” is hearty, comforting, and incredibly delicious. Rich beef stock, is kissed with vermouth and brandy then simmered with caramelized onions. Crisp garlic infused croutons, and melted Gruyere cheese are melted on top. What’s not to love?
This recipe for French onion soup is from Julia Child’s The Way to Cook. This is one of my favorite go-to cookbooks as they are classic French dishes with clear instructions. Mastering the Art of French Cooking is a great basic cookbook as well. (This recipe was originally published January 16th, 2012. As an Amazon Affiliate, I earn commission on qualifying purchases.)
Why this recipe works
Although French onion soup sounds fancy, it really is a simple soup. With minimal ingredients, the hardest part is waiting for the onions to caramelize. Unlike some recipes I’ve seen for “French onion soup”, this one does not contain either Worcestershire sauce or soy sauce. I’m not sure how this became a “thing”. Worcestershire sauce is a British condiment and soy sauce is Asian. There is no need to add them to a recipe for classic French onion soup!
What kind of onions do you use in French onion soup?
If you want to make this classic recipe yellow onions are best. Yellow onions lend themselves to a long slow cooking like stews or soups. Red onions are best raw or quickly pickled.
What kind of cheese is best for French onion soup?
Traditionally a Swiss Gruyere cheese is used. If you have trouble finding gruyere, substitute Swiss cheese. You can either slice it or shred it. I’ve found Trader Joe’s Swiss & Gruyere shredded blend works well and won’t break the bank.
How is it thickened?
French onion soup is thickened with a small amount of flour, just 2 Tablespoons. You definitely want a thin, brothy soup, so it’s just enough flour to give the soup some body.
Can you make French onion soup gluten free?
Absolutely! I’ve made it gluten free a couple of ways. You can substitute gluten free all-purpose flour blend, or if you’re grain free, skip it all together. You can just add the cheese to the finished soup without the crouton too, but the cheese sort of sinks to the bottom.
How do you caramelize onions?
Caramelized onions are a wonderful thing! Sometimes I’ll make extra caramelized onions so I can have them for this Brie and Fig Jam appetizer with caramelized onions. So good! The key to caramelizing onions is to let them cook slowly. At first there will be a lot of liquid, but as it evaporates, the onions will start to cling to the bottom of the pot and turn a lovely golden brown. Stir them occasionally. Just a 1/2 teaspoon of sugar helps the caramelization process.
Do you use red or white wine for French onion soup?
Actually, for this recipe Vermouth and brandy are used. Vermouth is a fortified wine and is great to have on hand for cooking. It’s perfect for deglazing a pan and making a quick sauce and it keeps well in the cupboard, which means you don’t have to open a bottle of wine every time you need wine in a recipe. You can absolutely omit both the wine and brandy if you’re sensitive, but it does cook a long time and the alcohol burns off.
What sort of bread is best for the crouton?
Naturally a good French baguette is best! You can serve the rest of the loaf on the side or with another soup! (For the nutritional value, I’ve only included a half of a baguette since you’ll only need a slice or two for each bowl.
What’s the easiest way to slice the onions?
Ok, this recipe calls for 2 1/2 pounds of sliced onions. You can absolutely cut them by hand or use a food processor or mandoline and slice them nice and thin in about 5 minutes. I love this mandoline! It also makes great French fries.
What’s the best way to serve French onion soup?
How do you make French onion soup?
Step 1: Slice the onions thinly. Using a mandoline or food processor makes this task go quickly. But I can’t help with the tears!
Step 2: Heat the butter and olive oil over a moderate heat. Heating both these fats together prevents the butter from burning. Add all the sliced onions. It’ll seem like a lot of onions, but just like spinach, they’ll cook way down!
Step 3: The onions need to cook for a while. First the liquid will evaporate, then they’ll start to brown. Add the sugar and salt at this step. Stir them every once in a while. You’ll want to brown them, not burn them.
Step 4: Once the onions are a nice deep golden brown, add the flour and cook a couple of minutes.
Step 5: Add 2 cups of hot stock. The stock or broth should be hot to help incorporate the flour. Once you’ve added and blended the 2 cups of stock, add the remaining stock, vermouth and brandy. Add a sprig of fresh thyme.
Step 6: Loosely cover the pot and reduce the heat to low, simmering very slowly for about 1 1/2 hours. If the soup reduces too quickly or by too much, add more broth.
Step 7: Check the seasoning. Why wait? Because as the soup reduces, the flavor intensifies. Season to taste with black pepper and kosher salt if needed.
Step 8: Pre-heat the broiler. Slice the baguette on the diagonal into 3/4″ slices.
Brush each side of the bread with olive oil, then rub each side with the cut end of a clove of garlic. Toast the bread until golden brown on each side.
Step 8: Fill soup bowls, place on a cookie sheet.
Cover each bowl with one or two slices of toasted bread and then a handful of grated cheese. Place cookie sheet under broiler.
Keep and eye on it. The cheese will melt quickly! Careful when serving as the soup bowls will be very hot!
French Onion Soup Gratine
- 1 small baguette cut into 3/4" thick slices and toasted
- 1 cup Grated Gruyere or Swiss cheese
- 1 clove garlic
- 2 Tablespoons olive oil
- Using a heavy bottomed saucepan, heat the oil and butter over a moderate heat.
- Add the onions and cover. Cook over a low heat until tender and translucent, about 10 minutes.
- Stir in salt and sugar, raise heat to moderately high and let the onions brown, stirring frequently until they are a golden walnut color, 35 to 40 minutes.
- Add flour and cook slowly, stirring, for another 3 to 4 minutes. Remove from heat, let cool a moment, then whisk in 2 cups of hot stock.
- When well blended, bring to a simmer, add the rest of the stock, the brandy or Cognac and the vermouth. Add a sprig of fresh thyme.
- Cover loosely and simmer very slowly 1 1/2 hours, adding a little more broth if the liquid reduces too much.
- Adjust seasoning. At this point taste the broth and decide if it needs any more salt or pepper.
- To finish the soup, brush both sides of the bread slices with olive oil, then rub the cut side of a clove of garlic over both sides. Toast under a broiler, flipping until both sides are golden brown.
- Ladle soup into oven proof bowls. Preheat broiler.
- Float one or two croutons on top of the soup to cover.
- Top with grated cheese. Place bowls on a sheet pan.
- Place under the broiler, watching carefully, since it will brown fast! Broil until cheese is melted and light golden brown.
- Slice baguette on the diagonal, about 3/4" thick.
- Brush each side of the bread slices with olive oil and rub with cut garlic clove.
- Make ahead tip: the onions can be caramelized the day before and refrigerated.