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1
Special equipment: eight 12-ounce soup crocks
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2
Melt the butter in a very large Dutch oven or pot over medium heat.
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3
Add half the onions and sprinkle with 1/2 teaspoon salt and a few grinds of black pepper.
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4
Top with the remaining onions and sprinkle with 1/2 teaspoon salt and more pepper.
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5
Add the bay leaves and thyme and cook, stirring occasionally, until the onions are very soft and just begin to turn brown, about 1 hour.
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6
(The onions will begin to stick to the bottom of the pan and turn brown after about 30 minutes; just keep scraping them up and stirring them into the rest of the onions.)
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7
Add the wine to the pot, bring to a simmer and cook until it has almost completely evaporated, about 4 minutes.
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8
Add the beef broth and 1 cup of water, bring to a simmer and cook until the flavors have come together and the soup is rich, about 45 minutes.
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9
Season with 1/2 teaspoon salt and a few grinds of black pepper.
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10
Either keep the soup warm on a low burner or cool completely, refrigerate and reheat later.
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11
(The cooked soup can be refrigerated for up to 2 days or cooled and frozen for up to 1 month.)
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12
Preheat the broiler.
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13
Place four soup crocks on a rimmed baking sheet and fill them about 3/4 of the way with hot soup.
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14
Float a slice of bread on top of each and cover with Gruyere.
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15
Broil until the Gruyere is golden brown (don't be alarmed if some soup bubbles out), 2 to 3 minutes.
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16
Repeat with the remaining soup, bread and Gruyere.
