VEGETARIAN FRENCH ONION SOUP WITH MUSHROOMS

Vegetarian French Onion Soup with Mushrooms image

Provided by Martha Stewart

Time 1h

Number Of Ingredients 9

3/4 stick unsalted butter
2 large onions, peeled, halved, and thinly sliced (about 4 cups)
2 bunches scallions, white and light-green parts coarsely chopped (about 3/4 cup), dark-green tops thinly sliced
4 sprigs thyme, plus leaves for serving
1 dried bay leaf
12 ounces cremini mushrooms, coarsely chopped
Coarse salt and freshly ground pepper
4 1 1/4-inch-thick slices sourdough bread
1 1/2 cups shredded Gruyere (about 4 ounces)

Steps:

Melt butter in a medium pot over medium-high heat. Add onions, chopped scallions, thyme sprigs, and bay leaf. Cook, stirring frequently and gradually lowering heat to prevent scorching, until onions are soft and golden brown, about 20 minutes. Stir in mushrooms; season with salt and pepper. Cook, stirring occasionally and scraping browned bits from bottom of pan, until mushrooms have released most of their moisture, about 15 minutes. Stir in 4 cups water and bring to a boil; reduce heat and simmer 5 minutes. Discard thyme sprigs and bay leaf; season with salt and pepper.
Preheat broiler with rack 6 inches from heating element. Divide soup among 4 ovenproof bowls. Top each with a bread slice; sprinkle with cheese. Broil until cheese is melted and golden brown in spots, 2 to 3 minutes. Sprinkle with thyme leaves and scallion tops.