French Onion Soup with a Porcini Twist

1. Rehydrate Porcini Mushrooms

Begin by rehydrating 1 ounce of dried porcini mushrooms in a saucepan filled with enough water to cover them. Let them soak while you move on to the onions, allowing the mushrooms to become plump and tender.

2. Cook Onions

In a large Dutch oven, heat 4 tablespoons of unsalted butter and 2 tablespoons of olive oil over low heat. Once the butter has melted, add 4 large, thinly sliced yellow onions. Season with a pinch of kosher salt and black pepper. Cook the onions for about 15 minutes, stirring occasionally until they begin to wilt and soften.

3. Caramelize Vegetables

Turn up the heat to medium-high and continue to cook the onions for another 15 minutes, or until they become beautifully golden and aromatic. Add in a thinly sliced large fennel bulb and a similarly sliced leek or two, with a bit more salt to taste. Saute these vegetables together for an additional 15 minutes, allowing the flavors to meld.

4. Brown Vegetables and Make Roux

Increase the heat to high and let the vegetables brown for approximately 5 minutes. Sprinkle 2 tablespoons of all-purpose flour over the browned vegetables, stirring for about 1 to 2 minutes to cook off the raw flour taste and create a roux.

5. Deglaze and Simmer Soup

Chop the rehydrated porcini mushrooms and add them to the pot along with 1 cup of dry white wine, 2 large fresh thyme sprigs, and a bay leaf. Let the wine reduce slightly by cooking for 2 to 3 minutes. Pour in the reserved mushroom liquid and 2 quarts of beef stock. Allow the soup to simmer for about 30 minutes.

6. Prepare Bread and Cheese Topping

Place 6 slices of toasted sourdough or peasant bread on a baking sheet and generously top them with 1.5 cups of grated Gruyère and 0.75 cups of grated Parmesan. Bake in the oven at 375 degrees Fahrenheit until the cheese is melted and bubbly, about 15-20 minutes.

7. Serve Soup

Before serving, remember to remove the thyme sprigs and bay leaf from the soup. Ladle the soup into bowls, top each with a slice of the cheesy bread, and serve immediately.