Pressure Cooker French Onion Soup

Ingredients

• 6 tablespoons unsalted butter, plus more for toasts
• 3 pounds yellow or mixed onions, sliced 1/8 inch thick
• 1/2 teaspoon baking soda
• Kosher salt and freshly ground black pepper
• 1/2 cup dry sherry, such as Amontillado
• 2 quarts homemade or store-bought low-sodium chicken stock
• 2 sprigs thyme
• 1 bay leaf
• 1 teaspoon Asian fish sauce, optional
• 1 teaspoon cider vinegar
• 8 bowl-size slices rustic bread, toasted until crisp
• 1 medium clove garlic
• 1 pound Gruyère cheese, grated
• Freshly minced chives, for garnish

Directions

1. Warm the butter in an electric or stovetop pressure cooker set over medium heat. Stir in the onions and baking soda, then add salt and pepper. Cook, stirring as you go, until the onions begin to soften a bit and give off liquid, about 3 minutes.
2. Lock the cooker, bring it up to high pressure, 12.5 to 15 psi, and cook for 20 minutes. Vent the steam to release the pressure, then open the lid.
3. With the lid off, keep cooking and stir constantly until the liquid in the pot has cooked away and the onions look very dark, glossy, and sticky, about 5 minutes.
4. Pour in the sherry and let it come to a simmer, using your spoon to loosen the browned bits from the pot. Cook until the sharp alcohol aroma has mostly faded, about 3 minutes.
5. Add the stock, thyme, and bay leaf. Increase the heat to medium-high and bring the soup to a simmer, then reduce the heat and simmer for 10 minutes.
6. Stir in the fish sauce, if using, along with the cider vinegar. Taste and add salt and pepper if needed, then remove and discard the thyme sprigs and bay leaf.
7. To serve, heat the broiler and place the oven rack in the top position. Spread butter on the toasts, then rub them with the garlic clove until they smell fragrant. Ladle a little broth into the bottoms of 4 ovenproof serving bowls, and place half the toasts over it. Scatter some grated Gruyère over the toasts, then ladle in more soup and onions until the bowls are nearly full.
8. Place the remaining 4 toasts in the bowls, pressing them down so they are almost submerged. Cover with the rest of the grated cheese and arrange the bowls on a rimmed baking sheet. Broil until the cheese has melted and browned in patches. Finish with chives and serve.