French onion soup is one of those recipes that feels timeless—slow, cozy, and deeply comforting. But as with many classics, once you understand the why behind the method, it becomes a playground for creativity.
This version leans into layers of sweetness and aroma by using onion, leek, and fennel together. Each brings its own personality: onion for depth, leek for softness, and fennel for a subtle, almost floral sweetness. White wine and a touch of sherry add richness, while Herbes de Provence infuses the broth with herbal warmth instead of heaviness.
The key lesson here? Balance. When caramelized vegetables push the soup too sweet, salt and acid are your best friends. A splash of vinegar at the end wakes everything up and brings the soup back into harmony—proof that great cooking is often about small, thoughtful adjustments.
This is a French onion soup for everyday cooking: elegant, adaptable, and deeply satisfying without being fussy.
French onion soup is built on patience. Slow heat. Gentle caramelization. Letting vegetables do the work instead of rushing them. In this version, I leaned into layers of allium flavor by using onion, shallot, leek, and fennel—each bringing something different to the pot.
Shallots add a soft, almost wine-like sweetness. Leeks bring a mild, rounded depth. Fennel offers a subtle aromatic note that lifts the whole soup. Once everything is deeply caramelized, white wine and a splash of sherry deglaze the pot and pull every bit of flavor forward.
Seasoned with Herbes de Provence, this soup simmers into something warm and comforting—but also bright and herbal. And like many slow-cooked soups, balance matters. With so many naturally sweet vegetables, a final splash of vinegar and enough salt are what bring the soup back into focus.
This is French onion soup through a modern lens: familiar, flexible, and built on intuition rather than rules.
Ingredients
2 large yellow onions, thinly sliced
2 shallots, thinly sliced
1 large leek, cleaned and thinly sliced (white and light green parts)
2-3 tsp sherry vinegar or red wine vinegar (to taste)
Directions
Caramelize the Vegetables
Heat olive oil or butter in a large pot over medium-low heat. Add onions, shallots, leeks, and fennel. Sprinkle salt on them. Cook slowly, stirring often, for 35–45 minutes until deeply golden and caramelized. Add garlic the last minute stirring constantly.
Deglaze
Add white wine and sherry, scraping up any browned bits from the bottom of the pot. Let the liquid reduce until nearly evaporated and the vegetables look glossy.
Simmer
Add broth and 1 teaspoon Herbes de Provence. Bring to a gentle simmer, cover, and cook for 20–25 minutes.
Season & Balance
Stir in remaining ½ teaspoon Herbes de Provence. Season generously with salt and pepper. Add vinegar a little at a time, tasting until the sweetness is balanced and the soup feels savory and bright.
Serve
Serve warm with crusty bread, or finish with toasted bread and melted Gruyère if desired.
Recipe Note
Use a Food processor with the slicer attachment for a quick job slicing the vegetables
When cooking with multiple sweet alliums (onion, shallot, fennel), salt early and adjust acid at the end. Vinegar doesn’t make the soup taste sour—it sharpens everything else.
