Tip: I always start with an onion or two more than I need, because due to the vagaries of buying onions from grocery stores in the middle of winter, I never know when I’ll get one kind of banged up inside, except reliably any time I don’t buy extras.
- 3 pounds thinly sliced yellow onions (see Tip)
- 3 tablespoons unsalted butter
- Fine sea salt
- 1/4 cup dry sherry, vermouth, or white wine (optional)
- 1 bay leaf or a few sprigs of thyme (optional, and honestly, I rarely bother)
- 2 quarts (8 cups) beef, chicken, or vegetable (mushroom is excellent here) stock, the more robust the better
- Freshly ground black pepper
- 1 garlic clove
- One (3/4- to 1-inch) thick slice of bread for each bowl of soup
- 1/4 cup grated gruyere, comte, or a mix of gruyere and parmesan per toast
Uncover the pot, raise the heat slightly and stir in salt — I start with between 1 and 2 teaspoons of fine sea salt, or twice as much kosher 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.
[What? That range is crazy. Stoves vary so much, even my own. If your onions are browning before 40 minutes are up, reduce the heat to low, and if that’s still cooking too fast, try a smaller burner. The longer you cook the onions, the more complex the flavor, but when you’re happy with it, you can stop — the ghost of Julia Child will not haunt you, the Shame Wizard will not taunt you or anything.]
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. Partially cover pot and simmer for 15 to 20 minutes. Taste and adjust seasoning as needed; discard thyme sprigs and bay leaf if you used them.
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. You can eat it right away but it’s going to stay hot for a good 10 minutes or so, if you need more time.