Bet you’ve never tasted a French onion soup like this before! This recipe combines the classic French onion soup with a twist of pho broth for an umami-packed experience. Slow caramelized onions, fragrant garlic, and melted Gruyère or Swiss cheese make this dish cozy, cheesy, and absolutely irresistible.
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Melt butter in a large pan over medium-low heat. Add onions and sugar. Cook slowly, stirring occasionally, until deep golden brown and sweet—about 25–30 minutes. Don’t rush this step; the flavor comes from slow caramelization.
Add garlic to the onions and cook 1–2 minutes until fragrant. Pour in pho broth (and its seasonings) and water, add fish sauce if using, and simmer gently for 10–15 minutes. Taste and adjust salt and pepper.
Toast baguette slices in the oven until lightly golden.
Ladle soup into oven-safe bowls. Place a slice or two of toasted baguette on top, sprinkle generously with cheese. Broil until cheese melts and bubbles.
Garnish with herbs if desired. Eat immediately while cheesy, hot, and fragrant.
Don’t rush the caramelization process for the onions; it’s key to achieving the deep, sweet flavor.
Use oven-safe bowls for broiling the cheese to avoid any mishaps.
If you don’t have pho broth, you can substitute with regular beef or chicken broth, but the flavor will differ.
For a vegetarian version, use vegetable broth and skip the fish sauce.
Experiment with garnishes like Thai basil or cilantro for a fresh twist.
Can I use a different type of cheese?
Yes, Gruyère or Swiss cheese is recommended for its melting properties, but you can use mozzarella or cheddar as alternatives.
What can I substitute for pho broth?
You can use regular beef or chicken broth, but the flavor profile will be less complex.
How long should I caramelize the onions?
Caramelize the onions for 25–30 minutes over medium-low heat to achieve a deep golden brown color and sweet flavor.
Can I make this soup vegetarian?
Yes, use vegetable broth instead of beef or chicken pho broth and skip the fish sauce.
What bread works best for this recipe?
A small baguette or any crusty bread works well for soaking up the soup and holding the melted cheese.
Sandra is the face behind @SaffronandTarragon who shares approachable, globally-inspired recipes with practical tips and honest, relatable moments.
