cook · lunch · french

French Onion Soup

Name: French Onion Soup
Cuisine: french

Real French onion soup lives or dies by the onions. Rush them and you get watery broth with blonde onion bits. Take the time to caramelize them properly and you build the deep, sweet foundation that makes this soup worth the wait.

Total time: 1 hr 30 min
Hands-on: 1 hr 15 min
Serves: 6
Difficulty: Intermediate

Before you start

Low and slow wins this race

The onions need at least 45 minutes of slow cooking to caramelize properly. Don't rush this step — the difference between good and great French onion soup happens in those final 15 minutes when the onions turn bronze.

large heavy-bottomed pot
ladle
oven-safe bowls
cheese grater

Ingredients

3 lb yellow onions, sliced thin
4 tbsp butter
1 tbsp olive oil
1 tsp salt
1 tsp sugar
1/2 cup dry white wine
6 cups beef stock
2 tbsp fresh thyme
2 bay leaves
6 slices day-old baguette, 1-inch thick
2 cups Gruyère cheese, grated
1/2 cup Parmesan cheese, grated

Caramelization

Cook until the onions stick slightly

When properly caramelized, onions will stick lightly to the bottom of the pot and release easily when stirred. This fond builds the deep flavor that makes the soup.

Step by step

Start the onions. Heat butter and oil in a large heavy pot over medium heat. Add onions and salt, stirring to coat. Cook uncovered, stirring every 10 minutes.
Caramelize slowly. After 30 minutes, add sugar and reduce heat to medium-low. Continue cooking 15-20 minutes until onions are bronze and jammy. They should stick slightly to the pot bottom but release when stirred.
Deglaze. Pour in wine and scrape up any browned bits. Cook until wine reduces by half, about 3 minutes.
Build the soup. Add beef stock, thyme, and bay leaves. Bring to a boil, then simmer 20 minutes. Remove bay leaves and taste for seasoning.
Prepare for broiling. Heat broiler. Toast baguette slices until golden. Ladle soup into oven-safe bowls, top each with a bread slice, then pile on Gruyère and Parmesan.
Broil and serve. Broil 2-3 minutes until cheese bubbles and browns in spots. Serve immediately while cheese is still molten.

Tips & troubleshooting

Slice onions pole to pole, not across the equator, so they hold their shape while cooking
If onions start browning too quickly, lower heat and add a splash of water
Day-old bread holds up better under the broiler than fresh
Make the soup base a day ahead — the flavors improve overnight

Variations

Vegetarian Version. Use mushroom or vegetable stock instead of beef. Add a splash of soy sauce for umami depth.
Classic Cognac. Replace wine with 1/4 cup cognac for traditional French bistro flavor.
Mixed Cheese. Combine Gruyère with aged cheddar or Comté for different melting characteristics.

Questions

Can I use a different type of onion?: Yellow onions work best for their balance of sweetness and sharpness when caramelized. Sweet onions like Vidalia will work but lack some depth.
What if I don't have oven-safe bowls?: Toast the cheese-topped bread separately under the broiler, then float it on top of the soup in regular bowls.
How do I know when the onions are properly caramelized?: They'll be bronze colored, jammy in texture, and taste sweet with no sharp bite. The process takes at least 45 minutes — don't rush it.