Soufflé Topped Onion Soup
- 2 T olive oil
- 3 large yellow onions, very thinly sliced
- 1 pn freshly ground black pepper
- 2 t plus 1/2 teaspoon kosher salt
- 1/4 c plus 2 tablespoons white wine
- 8 c chicken broth or stock
- 1 dried bay leaf
- 2 t fresh thyme leaves
- 1 T sugar
- 1 T plus 1 teaspoon fresh lemon juice
- 6 sli soft white bread
- 4 T unsalted butter
- 4 T all-purpose flour
- 1 1/2 c whole or part-skim milk
- 1 1/2 c grated gruyère cheese, plus 6 thin slices
- 1 pn cayenne pepper
- 6 oz large egg whites
- 1/4 c grated parmesan
Preheat oven to 350 degrees.
In a large saucepan, warm the olive oil over medium heat. Add the onions, pepper and 2 teaspoons salt. Cook over low heat, partially covered, stirring occasionally, until well-caramelized, 30 to 40 minutes. Raise heat to high and add the ¼ cup wine, scraping up any onion bits from the bottom of the pan. Boil for 1 minute. Add the stock, bay leaf and thyme. Bring to a boil, reduce heat to low, and simmer for 20 minutes. Stir in sugar and 1 tablespoon lemon juice. If not using right away, allow soup base to cool to room temperature and refrigerate.
While soup base simmers, trim the bread to fit inside individual soup bowls about 5 inches in diameter. Place trimmed bread slices on a baking sheet and toast in oven until lightly golden, about 10 minutes. Remove from oven and set aside. If making ahead, cool and store in a sealable plastic bag at room temperature.
Make the soufflé batter: In a large saucepan, melt butter over medium-low heat. Add flour and whisk continuously, until the roux is well blended and beginning to bubble. Add half of the milk, whisking continuously, until the milk is completely blended and there are no lumps. Repeat with the remaining milk. Raise the heat so that mixture is gently bubbling. Continue to whisk until sauce is smooth, shiny and thickened to the consistency of pudding, about 4 minutes. Add the grated Gruyère cheese and stir until completely melted into the sauce. Stir in the cayenne, 2 tablespoons wine, 1 teaspoon lemon juice and ½ teaspoon salt. Remove from heat and set aside; or, if using later, cool, cover with plastic wrap and refrigerate.
About 15 minutes before you want to serve the soup, preheat the oven to 400 degrees. Gently reheat the onion soup base over medium heat. Season again with lemon juice and salt, if needed. Remove from heat.
In a large bowl with an electric mixer, beat the egg whites to a medium-stiff peak. Pour the soufflé batter into another large bowl. With a rubber spatula, gently fold in 1/3 of the egg whites into the batter. Repeat with remaining egg whites and stir the Parmesan cheese, folding the mixture until completely combined.
Fill ovenproof soup bowls ¾ full of soup. Top with 1 crouton and then a slice of Gruyère. Using a rubber spatula, gently spoon 1/6 of the soufflé batter onto the crouton. Carefully place the soup bowls onto a baking sheet and transfer to the oven. Bake until the soufflé is well-risen and golden brown, about 20 minutes. Serve immediately.