Sarra Ina Garten’s onion fennel soup gratin is a rich, caramelized French onion soup made with 3 pounds of Spanish onions, 2 pounds of fresh fennel, dry sherry, Cognac, white wine, beef broth, and a bubbly Gruyère and sourdough bread topping broiled until golden. The onions and fennel cook low and slow for 30 to 40 minutes before the three spirits go in. It serves 4 to 6 and takes about 1 hour 30 minutes.
This recipe comes from How Easy Is That?, where Ina says she loves to “take a classic recipe and turn up the volume.” Her upgrade to classic French onion soup is the fennel, which adds a subtle anise sweetness that deepens the caramelized onion flavor. Three separate spirits layered in at different stages, sherry and Cognac first, then white wine, build a complexity that a single splash of wine can’t match.
The 30 to 40 minutes of cooking the onions and fennel is what makes or breaks this soup. You need them golden brown, not just translucent. That long, slow browning develops the caramelized sugars that give the broth its deep amber color and sweet, savory backbone. Pull them off at 15 minutes when they’re still pale and the soup tastes thin and flat no matter how much broth and wine you add later.
Ina Garten Onion Fennel Soup Gratin Recipe
Course: Soups6
servings15
minutes1
hour15
minutes400
kcalIna’s spin on classic French onion soup gratinée from How Easy Is That?, with fresh fennel layered in alongside the onions and three spirits building flavor in stages. The broiled Gruyère and sourdough topping is the same gooey, crusty lid you expect from a French onion soup, but the fennel underneath changes everything. Make it as a first course or double the bread and cheese for a full dinner.
Ingredients
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4 tablespoons (55g) unsalted butter
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1/4 cup (60ml) good olive oil
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3 lb (1.4kg) Spanish onions, halved and sliced 1/4 inch thick
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2 lb (900g) fresh fennel, tops and cores removed, sliced 1/4 inch thick
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1/2 cup (120ml) good dry sherry
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1/2 cup (120ml) Cognac or brandy
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1 1/2 cups (360ml) good dry white wine, such as Sauvignon Blanc
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8 cups (1.9L) canned beef broth
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3 bay leaves
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1 tablespoon kosher salt
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1 1/2 teaspoons freshly ground black pepper
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1 small sourdough or white French boule, crusts removed, sliced
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1/2 inch thick and toasted
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4 to 6 oz (115 to 170g) Gruyère cheese, grated
Directions
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Caramelize the onions and fennel: Heat the butter and olive oil in a large stockpot over medium-high heat. Add the onions and fennel and cook over medium heat for 30 to 40 minutes, stirring occasionally, until the onions turn a deep golden brown. If they aren’t browning after 20 minutes, turn the heat up.
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Deglaze with spirits: Add the sherry and Cognac, scraping up all the brown bits stuck to the bottom of the pot. Simmer uncovered for 5 minutes. Add the white wine and simmer uncovered for 15 more minutes so the alcohol cooks off and the flavors concentrate.
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Simmer the broth: Add the beef broth, bay leaves, salt, and pepper. Bring to a boil, lower the heat, and simmer uncovered for 20 minutes. Remove the bay leaves and taste for seasoning.
- Broil the gratin topping: Preheat the broiler and position a rack 5 inches below the heat source. Ladle the soup into heatproof serving bowls. Top each bowl with toasted bread slices and sprinkle generously with grated Gruyère. Broil for 3 to 5 minutes until the cheese is melted, bubbly, and lightly browned. Serve immediately.
FAQs
Why does Ina add fennel to French onion soup?
Fennel has a mild anise sweetness that deepens as it caramelizes alongside the onions for 30 to 40 minutes. It adds a second layer of flavor that straight onion soup doesn’t have, with a subtle warmth that makes the broth taste more complex.
Ina says she wanted to “turn up the volume” on the classic. The fennel does that without competing with the onions. Once everything is browned and simmered, most people can’t identify the fennel as a separate ingredient. They just notice the soup tastes richer and more interesting than a standard French onion.
Why does the recipe use three different spirits?
Each one does a different job. The dry sherry and Cognac go in first to deglaze the pot, lifting all the caramelized bits off the bottom and adding warm, rounded depth. The white wine goes in next and simmers for 15 minutes, adding brightness and acidity that keeps the soup from tasting too heavy.
Layering them at different stages lets each spirit contribute its own character before the next one goes in. If you dumped all three in at once, the flavors would compete rather than build. The 5-minute sherry and Cognac simmer followed by the 15-minute wine simmer gives the alcohol time to cook off while leaving the flavor behind.
Can you make the soup base ahead and broil later?
The broth base keeps in the fridge for up to 3 days and actually improves overnight as the onion and fennel flavors meld into the beef broth. Make the full soup through the simmering step, cool it, and refrigerate.
When ready to serve, reheat the broth on the stovetop, ladle into heatproof bowls, add the toasted bread and Gruyère, and broil fresh. The gratin topping must be done right before serving because the cheese needs to be hot, bubbly, and slightly crusty. Reheating a broiled gratin turns the bread soggy and the cheese rubbery.
What kind of bread works best for the gratin?
Ina uses a sourdough or white French boule with the crusts removed, sliced 1/2 inch thick and toasted before it goes on the soup. The toasting step is critical because it gives the bread enough structure to hold up under the melted Gruyère without collapsing into the broth.
Dense, firm bread works best. Soft sandwich bread falls apart immediately. A country sourdough or pain de campagne with a tight crumb holds its shape under the cheese while still soaking up broth from below. Cut the slices to fit your bowls so the bread covers the surface like a lid, trapping the melted cheese on top.
How is this different from Ina’s Fennel Soup Gratin?
Ina actually has an earlier Fennel Soup Gratin from Barefoot Contessa Parties! (2001) that focuses on fennel as the main ingredient without the heavy onion component.
This Onion & Fennel Soup Gratin from How Easy Is That? (2010) shifts the balance: 3 pounds of Spanish onions with 2 pounds of fennel, making it a true French onion soup with fennel as the supporting player. The three spirits, sherry, Cognac, and white wine, also push this version in a more complex direction. If you want a fennel-forward soup, look for the Parties version. If you want an upgraded French onion soup, this is the one.
