Yield: 4 Servings

J. Kenji López-Alt / Serious Eats

Using traditional technique, caramelizing onions is a slow, painstaking process. Thirty minutes in the pressure cooker, though, and they taste just as good as if they had been on the stove for hours. Once they’re done, it just takes a few more minutes to make them into soup. Our recipe calls for a ton of Gruyère—French onion soup just isn’t right without a thick blanket of cheese.

• 6TBS unsalted butter, plus more for toasts
• 3lb yellow or mixed onions, sliced 1/8 inch thick (about 4 to 5 large onions) (see note above)
• ½tsp baking soda
• Kosher salt and freshly ground black pepper
• ½cup dry sherry, such as Amontillado
• 2quarts chicken stock
• 2sprigs thyme
• 1bay leaf
• 1tsp Asian fish sauce (optional)
• 1tsp cider vinegar
• 8bowl-size slices rustic bread, toasted until crisp
• 1medium clove garlic
• freshly minced chives, for garnish
• 1lb Gruyère cheese, grated

Onions:

Set a 6-qt Instant Pot to the SAUTÉ MEDIUM setting. Add butter and heat until foaming stops.

Add onions and baking soda and stir to combine. Season with salt and pepper. Cook, stirring, until onions slightly soften and start to release liquid, about 3 minutes.

Seal Instant Pot and set to MANUAL HIGH pressure for 20 minutes. Release pressure using Quick Release, then remove lid.

Continue cooking with lid off, stirring constantly, until liquid inside has completely reduced and the onions are deep brown and sticky, about 5 minutes.

Add sherry and bring to a simmer, scraping up any browned bits. Cook until alcohol smell is mostly gone, about 3 minutes. Add stock, thyme, and bay leaf, raise heat to medium-high, and bring to a simmer. Lower heat and simmer for 10 minutes.

Add fish sauce, if using, and cider vinegar and season with salt and pepper (if necessary). Discard thyme sprigs and bay leaf.

To Serve:

Preheat broiler and move oven rack to top position. Butter toasts and rub with garlic clove until fragrant. Spoon a small amount of broth into the bottoms of 4 ovenproof serving bowls, then top with half the toasts. Sprinkle some grated Gruyère on top of toasts, then spoon more soup and onions on top, nearly filling the bowls. Set the remaining 4 toasts in each bowl, pushing to nearly submerge them. Top with remaining grated cheese and set bowls on a rimmed baking sheet. Broil until cheese is melted and browned in spots.

Garnish with chives and serve.