Gratin Of French Onion Recipe

Prepare onions

Peel and thinly slice the yellow onions into half-moons about 3-4 mm thick. Aim for even slices so they caramelize uniformly.

Cook onions

In a large heavy-bottomed sauté pan or Dutch oven, melt the unsalted butter with the olive oil over medium heat. Add the sliced onions and spread them in an even layer. Sprinkle the granulated sugar and sea salt over the onions. Cook, stirring every 3-5 minutes, allowing onions to soften and begin to brown. Reduce heat to medium-low if they are browning too quickly. Total cooking time for deep, sweet caramelization is about 40-50 minutes.

Toward the end of caramelization, stir in the black pepper. The onions should be deeply golden-brown and jammy.

Deglaze

Increase heat to medium-high and pour in the dry white wine to deglaze the pan, scraping up browned bits stuck to the bottom. Let the wine reduce by about half, about 2-3 minutes.

Add broth and herbs

Add the beef broth, thyme sprigs, and bay leaf to the pot. Bring to a gentle simmer, then reduce heat and simmer uncovered for 10 minutes to meld flavors. Taste and adjust seasoning — add a splash (about 1 tbsp) of sherry here if using, and more salt if necessary.

Prepare croutons

While broth simmers, preheat oven to 200°C (400°F). Brush both sides of the baguette slices lightly with olive oil and place on a baking sheet. Toast in the oven until golden and crisp, about 8-10 minutes, flipping once. Rub the warm toasted slices with the halved garlic clove for a subtle garlic flavor.

Assemble cheese

Arrange the toasted croutons on top of individual oven-safe bowls or a single shallow gratin dish. Ladle the hot onion and broth mixture over the croutons, dividing evenly. Top each portion with sliced or shredded provolone and sprinkle with grated Parmesan.

Grill until bubbly

Preheat the oven broiler (grill). Place the assembled bowls or gratin dish on a baking sheet and slide under the broiler until the cheese is melted, bubbling and lightly browned, 2-5 minutes — watch closely to avoid burning.

Remove from oven, discard thyme sprigs and bay leaf. Garnish with chopped fresh parsley and serve immediately, taking care because the bowls and soup will be very hot.