French Onion Soup

Start the onions

Melt the butter in a wide heavy pot over medium heat. Add all the onions and the salt. The pot will look overfull. Stir until the onions are coated and let them collapse for 10 minutes.

Caramelize them slowly

Lower the heat to medium low and cook for 45 to 60 minutes, stirring every 5 minutes or so and scraping the brown film off the bottom. This is the whole dish and it cannot be rushed. High heat scorches the edges before the sugars develop and leaves a bitter soup. The onions are ready when the volume has dropped by about three quarters and the mass is deep mahogany, glossy, and jammy enough to hold a spoon track.

Deglaze the pot

Pour in the wine or sherry. Scrape the bottom clean as it bubbles and cook for 2 to 3 minutes, until the pot looks nearly dry again.

Simmer with stock and herbs

Add the stock, thyme, bay leaves, and pepper. Bring to a boil, then simmer uncovered for 25 to 30 minutes. Remove the thyme stems and bay leaves. Taste and add salt.

Toast the bread

Heat the oven to 400F (205C). Spread the baguette slices on a sheet pan and bake 8 to 10 minutes, until dry and crisp through the middle. Bread that is only warm will sink and dissolve.

Broil the bowls

Set the broiler to high. Put six oven-safe bowls on a sheet pan and ladle the soup in, leaving half an inch at the rim. Float two toasts on each and cover them edge to edge with Gruyere. Broil 2 to 4 minutes, until the cheese bubbles and browns in spots. Stand at the oven and watch the whole time, since the gap between browned and burnt is under a minute.