Active Time

　　45 min

　　Total Time

　　1 1/2 hr

　　This version of the classic is gorgeously cheesy, not gunky. Slow cooking gives the broth depth of flavor and a silky texture.

　　

Ingredients

Makes 6 (light main course) servings

　　2 lb medium onions, halved lengthwise, then thinly sliced lengthwise

　　3 sprigs fresh thyme

　　2 Turkish bay leaves or 1 California

　　3/4 teaspoon salt

　　1/2 stick (1/4 cup) unsalted butter

　　2 teaspoons all-purpose flour

　　3/4 cup dry white wine

　　4 cups reduced-sodium beef broth (32 fl oz)

　　1 1/2 cups water

　　1/2 teaspoon black pepper

　　6 (1/2-inch-thick) diagonal slices of baguette

　　1 (1/2-lb) piece Gruyère, Comte, or Emmental

　　2 tablespoons finely grated Parmigiano-Reggiano

　　

Special Equipment

6 (8- to 10-oz) flameproof soup crocks or ramekins; a cheese plane

　　

Step 1

Cook onions, thyme, bay leaves, and salt in butter in a 4- to 5-quart heavy pot over moderate heat, uncovered, stirring frequently, until onions are very soft and deep golden brown, about 45 minutes. Add flour and cook, stirring, 1 minute. Stir in wine and cook, stirring, 2 minutes. Stir in broth, water, and pepper and simmer, uncovered, stirring occasionally, 30 minutes.

　　

Step 2

While soup simmers, put oven rack in middle position and preheat oven to 350°F.

　　

Step 3

Arrange bread in 1 layer on a large baking sheet and toast, turning over once, until completely dry, about 15 minutes.

　　

Step 4

Remove croûtes from oven and preheat broiler. Put crocks in a shallow baking pan.

　　

Step 5

Discard bay leaves and thyme from soup and divide soup among crocks, then float a croûte in each. Slice enough Gruyère (about 6 ounces total) with cheese plane to cover tops of crocks, allowing ends of cheese to hang over rims of crocks, then sprinkle with Parmigiano-Reggiano.

　　

Step 6

Broil 4 to 5 inches from heat until cheese is melted and bubbly, 1 to 2 minutes.

　　Cooks' note:

　　Soups and croûtes can be made 3 days ahead (but do not add croûtes and cheese to soup); cool completely, uncovered, then chill soup, covered, and keep croûtes in an airtight container at room temperature. Reheat soup before proceeding with recipe.