French Onion Soup with Cheesy Sourdough Toast

Name: French Onion Soup with Cheesy Sourdough Toast
Prep time: 10 min
Cook time: 5 h
Total time: 5 h 10 min
Yield: 2 servings
Cuisine: French
Ingredients: 4 large onions, chopped; 4 tbsp butter; 1 tsp umami seasoning blend; 2 bay leaves; 4 cups beef stock; 2 thick slices sourdough bread; 1/2 cup shredded provolone cheese; 1/2 cup shredded mozzarella cheese; 1 tbsp chopped chives, for garnish

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This French onion soup features deeply caramelized onions simmered in beef stock and finished with a generous slice of cheesy sourdough toast instead of traditional croutons, delivering rich umami flavor and satisfying texture.

🌍French 🏷️French onion soup 🏷️Soup 🏷️Caramelized onions 🏷️Comfort food

🏷️Cheesy

🏷️Sourdough

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Total

5h 10m

Servings

2

Recipe Source

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Ingredients

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9 Ingredients

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Instructions

1
Roughly chop the onions.
2
Preheat your oven to 350°F (175°C).
3
Place the chopped onions in a large, oven-safe pot or Dutch oven and dot the top with butter.
4
Cover the pot and place it in the preheated oven to bake for 3 hours.
5
Every hour, remove the pot from the oven and stir the onions to ensure they cook evenly and don't burn.
6
After 3 hours, the onions should be deeply caramelized. Remove the pot from the oven and place it on the stovetop over medium heat.
7
Season the onions with the umami seasoning blend and add the bay leaves.
8
Pour in the beef stock, stirring to combine and scrape up any browned bits from the bottom of the pot.
9
Cover the pot, reduce the heat to low, and let the soup simmer for at least 2 hours to allow the flavors to meld.
10
Towards the end of the simmering time, toast the sourdough slices.
11
Grate the provolone and mozzarella cheeses.
12
Top the toasted sourdough with the shredded cheese blend and place on a baking sheet.
13
Broil the cheesy toast for about 3 minutes, or until the cheese is melted, bubbly, and lightly browned.
14
Ladle the hot soup into bowls. Garnish the cheesy toast with chopped chives and serve alongside the soup for dipping.

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Tips & Notes

Pro tips

Cook onions low and slow over medium heat, stirring every 5 minutes. Patience yields sweet, deeply golden onions—rushing creates bitter or unevenly cooked results.
Toast the sourdough bread before adding cheese so it stays crisp underneath the melted cheese layer rather than becoming soggy.
Use a high-quality beef stock; it's the backbone of this soup. Low-sodium stock lets you control salt and prevents an overly salty final dish.
Garnish with fresh chives just before serving to add brightness and cut through the richness of the melted cheese.

Substitutions

Beef stock → chicken or vegetable stock (result will be lighter and less rich)
Sourdough bread → crusty baguette slices or focaccia (texture remains crispy)
Provolone + mozzarella → Gruyère alone (more traditional French preparation)
Umami seasoning blend → 1/2 tsp Worcestershire sauce + pinch of soy sauce (similar depth)

Storage & make-ahead

Store cooled soup in an airtight container for up to 3 days. Reheat gently on the stove; assemble fresh cheesy toast at serving time to prevent sogginess.

Common Questions

How long does it take to caramelize the onions properly?

Caramelizing onions typically takes 30–40 minutes over medium heat, stirring occasionally. Don't rush this step; it's essential for deep flavor development.

Can I make this soup ahead of time?

Yes. Prepare the soup base (onions and broth) up to 2 days ahead and refrigerate. Reheat gently before serving, then top with fresh cheesy sourdough toast.