Caramelize your onions: Melt butter in the bottom of a 5- to 6-quart saucepan over medium heat. Add the onions, toss to coat them in butter and cover the pot. Reduce the heat to medium-low and let them slowly steep for 15 minutes.

Uncover the pot, raise the heat slightly and stir in 1 TP salt — Cook onions, stirring every 5 minutes (you might be fine checking in less often in the beginning, until the point when the water in the onions has cooked off) for about 40 to 90 minutes longer.

Make the soup: Onions are caramelized when they’re an even, deep golden brown, sweet and tender. Add sherry or vermouth, if using, and scrape up any onions stuck to pan. Cook until it disappears. Add stock, herbs (if using), and a lot of freshly ground black pepper and bring soup to a simmer. Put in bay leaves. Partially cover pot and simmer for 15 to 20 minutes. Taste and adjust seasoning and herbs  as needed.

While soup is finishing, heat your broiler, and if you don’t have a broiler, heat your oven as hot as it goes. If your bread is not already stale (i.e. you did not leave the slices out last night to harden, probably because nobody told you to), toast them lightly, until firm. Rub lightly with a raw garlic clove. Line a baking sheet with foil and arrange soup bowls/vessels on top.

To finish: Ladle soup into bowls. Fit a piece of toast (trimming if needed) onto each. Sprinkle with cheese. Run under broiler until cheese is melted and brown at edges. Garnish with herbs.  (Original recipe by Smitten Kittchen).