French onion soup

Read through the recipe and gather the equipment. Use the ingredient lines to prepare and measure everything, and set an oven rack 6 inches below the broiler. Everything is sliced, grated and measured.

Melt the butter with the olive oil in the 5-quart to 6-quart Dutch oven over medium heat. When it foams, add the onions and 1 tsp kosher salt; the pot will be heaped. Cover and cook, bringing the bottom onions to the top every few minutes, until the onions have shrunk by about half, about 15 minutes.

Uncover the pot and turn the burner to medium-low heat. Stir every few minutes, scraping up the brown film on the bottom; whenever the film turns dark brown, add about 2 tablespoons of the water and scrape it loose. Cook until the onions are deep amber-brown, soft enough to smear and smell toasty-sweet, about 45 to 60 minutes.

Meanwhile, once the onions turn medium brown, heat the oven to 400°F with the rack 6 inches below the broiler for the toasts. The oven has reached temperature.

Stir the garlic into the onions over medium-low heat until you can smell it, about 30 seconds.

Sprinkle the flour over the onions and stir over medium-low heat until no dry flour shows, about 1 minute.

Raise the burner to medium heat and pour in the wine, scraping up the brown bits until the bottom of the pot is clean. Let it bubble until it is nearly gone and no longer smells sharp, about 2 to 3 minutes.

Add the broth, thyme sprigs and bay leaf. Bring the soup to a simmer over medium-high heat, then lower the heat so only a few bubbles break the surface. Simmer uncovered until the soup tastes strongly of onion, about 20 to 30 minutes.

Meanwhile, bake the baguette slices on the rimmed baking sheet on the rack 6 inches below the broiler at 400°F, turning once, until dry all the way through and golden at the edges, about 12 to 15 minutes. Move them to a plate.

Remove the thyme stems and bay leaf, then taste the soup. Aim for savory and deep, sweet but not sugary. If it tastes flat, add kosher salt to taste; if it tastes sweet or heavy, add the sherry vinegar a few drops at a time, up to 1 tsp, if using. Season with black pepper to taste. The soup tastes savory, deep and well seasoned.

Set the crocks on the rimmed baking sheet and ladle in the soup to 1/2 inch below the rims. Float 2 toasts in each crock and divide the Gruyère among them, covering the toasts to the edges. Then broil on high on the rack 6 inches below the broiler, watching the whole time, until the cheese is bubbling and browned in spots, about 2 to 5 minutes.

Set each crock on a plate with oven mitts and warn everyone that the crocks are very hot. Let the cheese settle for a moment, then serve as 4 servings. Each crock sits on a plate under a set cheese crust.