As posted on Boston.com

Serves 8

Ingredients:

• 4 tablespoons ( 1/2 stick) unsalted butter
• 3 pounds (about 9 large) yellow onions, thinly sliced
• Salt and pepper, to taste
• 1 baguette, sliced into thick rounds
• 1 teaspoon sugar
• 2 quarts beef stock
• 2 cups dry white wine
• 2 cups (about 1 pound) grated Gruyere cheese

1. Set the oven at 375 degrees.
2. In a large, heavy-based soup pot, melt the butter over medium heat. Stir in the onions, salt, and pepper. Cover and cook, stirring occasionally, for 15 minutes or until the onions soften and release their juices.
3. Meanwhile, arrange the sliced baguette on a baking sheet. Toast for 10 minutes or until browned. Turn the oven off.
4. Increase the heat under the onions to medium-high. Add the sugar and cook, stirring often, for 10 to 15 minutes or until the onions brown.
5. Add 2 cups of the stock and stir, scraping the browned bits from the bottom of the pan. Add the remaining stock and the wine. Bring to a boil. Lower the heat and simmer for 40 minutes. Taste for seasoning and add more salt and pepper, if you like.
6. Set the oven at 400 degrees. Ladle the soup into 8 large heatproof bowls. Add a slice or two of baguette to each one. Sprinkle with the cheese. Set the bowls on 2 large rimmed baking sheets and return to the oven. Bake for 10 minutes or until the cheese melts and browns.