6 large onions
2 teaspoons of dried thyme
2 Turkish bay leaves
3/4 teaspoon salt
1/2 stick (1/4 cup) unsalted butter
2 teaspoons all-purpose flour
4 cups reduced-sodium beef broth (32 fl oz)
1 1/2 cups water
1/2 teaspoon black pepper
For the topping
6 slices of wholemeal bread
1 (1/2-lb) piece sharp cheddar cheese
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 broth, water, and pepper and simmer, uncovered, stirring occasionally, 30 minutes.
While soup simmers, put oven rack in middle position and preheat oven to 350°F.
Arrange bread in 1 layer on a large baking sheet and toast, turning over once, until completely dry, about 15 minutes. Remove croûtes from oven and preheat broiler. Slice enough cheese (about 6 ounces total) with cheese plane to cover the bread, allowing ends of cheese to hang over the bread. Broil 4 to 5 inches from heat until cheese is melted and bubbly, 1 to 2 minutes.
Discard bay leaves and thyme from soup then float a croûte in each. Enjoy!