Petit Trois's French Onion Soup
Peer reviewed by UK recipe editorsAuthored by UK recipe editorsOriginally published 28 Jan 2026
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This classic French onion soup is the ultimate comfort food, offering a deep, savoury flavour that only comes from patience and high-quality ingredients. By slowly caramelising a generous amount of onions until they reach a rich amber hue, you create a complex sweetness that balances perfectly with the punchy dry Sherry and aromatic herbs. It is a timeless bistro favourite that brings a touch of Parisian elegance to your kitchen table.
While the process involves making a traditional stock from scratch, the depth of flavour achieved is well worth the effort. This hearty dish is perfect for a sophisticated dinner party starter or a warming weekend lunch. Topped with toasted baguette and a decadent layer of melted Gruyère and Emmental, it provides a satisfyingly salty finish that complements the silken onions beautifully.
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Ingredients for Petit Trois's French Onion Soup
2.7kg veal neck or beef bones
1 tablespoon grapeseed or vegetable oil
2 large onions, chopped
6 celery stalks, chopped
450g carrots, peeled, chopped
40g tomato paste
1 head of garlic, halved crosswise
4 sprigs thyme
1 bay leaf
3 tablespoons grapeseed or vegetable oil
1 tablespoon unsalted butter
1 head of garlic, halved crosswise
1.8kg onions, thinly sliced
Kosher salt, freshly ground pepper
3 tablespoons dry Sherry
6 sprigs thyme
1 bay leaf
4 1/2"-thick slices baguette, toasted
4 1/8"-thick slices Gruyere
4 1/8"-thick slices Emmenthal cheese
Cheesecloth
French onion soup bowls or 230g ramekins
How to make Petit Trois's French Onion Soup
Back to contentsPreheat oven to 218°C. Place a wire rack inside a rimmed baking sheet and place bones on top. Roast bones (undisturbed) until deep golden brown, 40–50 minutes. Transfer to a large pot and add 4.7L of water. Bring to a simmer, then use a fine-mesh sieve to skim off any foam or gray bits from the surface. Remove from heat.
Meanwhile, in another large pot, heat oil over medium-high. Add onions, celery, and carrots and cook, stirring occasionally, until vegetables start to caramelize, 10–15 minutes. Add tomato paste and cook, stirring often, until slightly darkened in colour, 6–8 minutes.
Add bones along with liquid, garlic, thyme, and bay leaf to vegetables. Bring just to a boil; reduce heat to low, and cook at a bare simmer, adding water as needed during cooking to maintain level of liquid until stock is flavorful, about 2 hours. Strain stock through a fine-mesh sieve into a large bowl, then strain again into another large bowl or airtight containers.
Stock can be made 5 days ahead. Let cool; cover and chill, or freeze up to 1 month ahead.
Heat oil and butter in a large pot over medium heat. Place garlic, cut side down, in pot and cook undisturbed until golden brown, about 4 minutes. Transfer garlic to a plate.
Add onions to same pot, season with salt and pepper, and cook, stirring occasionally at first and then more often as onions darken to keep them from getting too brown in any one spot, until golden but not mushy, 60–70 minutes (and no, this process can't be rushed at a higher temperature).
Add Sherry and stir, scraping up any browned bits from bottom of pot. Stir in 1925ml veal stock. Bundle up garlic, thyme, and bay leaf in cheesecloth and tie closed with kitchen twine. Add to pot; bring mixture to a boil. Reduce heat and cook, stirring occasionally, until liquid is reduced by one-quarter, flavours have melded, and onions are completely tender, 45–50 minutes.
Heat grill. Divide soup among bowls and top each with a toast and a slice each of Gruyere and Emmenthal cheese. Place on a rimmed baking sheet and grill until cheese is melted and brown in spots, about 5 minutes. Let cool for a minute or so before serving.
Disclaimer
While every effort has been made to ensure the information is accurate and up to date, individual needs may vary and dietary requirements can differ based on personal health conditions. Always check food labels and allergen information before preparing or consuming any recipe. If you have specific health concerns, allergies, intolerances, or are following a medically prescribed diet, seek advice from your GP, pharmacist, or a registered dietitian before making significant changes to your diet or lifestyle.
Article history
The information on this page is peer reviewed by qualified clinicians.
28 Jan 2026 | Originally published
Authored by:
UK recipe editors
Peer reviewed by
UK recipe editors

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