Caramelize the Onions:
In a large, heavy-bottomed pot (like a Dutch oven), heat the butter and olive oil over medium-low heat. Once the butter has melted, add the thinly sliced onions, salt, pepper, and sugar. Stir to coat the onions evenly. The sugar helps them caramelize, so be patient. Cook the onions, stirring occasionally, for about 30-40 minutes. The goal is to slowly soften and brown them to a deep, golden color without burning them. The onions should be soft and sweet when fully caramelized.

Add Garlic & Deglaze:
Once the onions are deeply caramelized, add the minced garlic and cook for an additional 1-2 minutes until fragrant. Pour in the white wine to deglaze the pot, scraping up any flavorful bits stuck to the bottom of the pot. Let the wine cook off for 3-4 minutes, reducing slightly.

Add the Broth & Simmer:
Pour in the beef broth and water, followed by the thyme and bay leaf. Bring the soup to a simmer over medium heat, then lower the heat and let it cook gently for 30-45 minutes. Taste and adjust seasoning with salt and pepper as needed. Remove the bay leaf before serving.

Prepare the Baguette:
While the soup simmers, preheat the broiler in your oven. Arrange the baguette slices on a baking sheet and toast them under the broiler for 1-2 minutes per side until golden brown and crispy.

Assemble the Soup:
Ladle the hot soup into oven-safe bowls or crocks (make sure they’re broiler-safe). Place one or two slices of toasted baguette on top of the soup in each bowl. Sprinkle a generous amount of shredded Gruyère cheese (and Parmesan if using) over the bread.

Gratinate the Soup:
Place the bowls under the broiler and cook for 2-3 minutes, or until the cheese is bubbling and golden brown. Keep a close eye on them so the cheese doesn’t burn.

Serve:
Garnish with fresh thyme sprigs for an extra touch of flavor and visual appeal. Serve immediately with a side of wine and enjoy the rich, comforting flavors of this quintessential French classic.

Tips:
Caramelizing the onions is the most important step in this recipe, so take your time and don’t rush it. The longer you caramelize, the deeper the flavor.

For a more complex flavor, you can add a splash of brandy or cognac when deglazing the onions.

Feel free to adjust the cheese blend to your liking, but Gruyère is the classic choice because it melts beautifully and adds that signature nutty, savory flavor.

This soup can be made in advance and stored in the fridge for up to 3 days, which makes it even better the next day! Just broil the bread and cheese just before serving.

Voilà! A classic French onion soup that’s sure to warm your soul. Enjoy it as a starter or a light meal. For a great wine pairing try Richard Rottiers Beaujolais Cru Moulin à Vent 2022, especially if adding a main course of Chicken or beef. If serving with lighted fair, say a caesar salad, a great pairing would be a Meursault Domaine Gilles Bouton Meursault 1er Cru 'Blagny' 2022