Slowly caramelizing onions in butter until they're golden brown makes the perfect base for homemade French Onion Soup. Beef stock and white wine provide rich flavor, and sherry adds depth and a touch more sweetness to the soup. It's a great project for a lazy afternoon, and dinner will be delicious!
5tablespoons(74grams)unsalted butter, divided, see Recipe Notes
3pounds(1kilogram)onions, yellow or sweet (Vidalia or Walla Walla, preferred), about 4 to 6 medium
2teaspoons (1teaspoon)kosher salt
½teaspoon(½teaspoon)black pepper
1½cups(360grams)dry white wine, see Recipe Notes
10sprigs(10sprigs)fresh thyme
2(2)bay leaves
4cups(960grams)beef stock, or store-bought low-sodium beef broth
2cups(454grams)water
½ to 1teaspoongranulated sugar, optional
For the topping
1(1)baguette, sliced
1(1)garlic clove, cut in half lengthwise
2teaspoons(2teaspoons)sherry, cognac, or cointreau (optional), see Recipe Notes
1cup(70grams)Gruyère, grated, see Recipe Notes
Instructions
Caramelize the onions: Cut the onions in half from the top to the root. Thinly slice the onions using a mandolin slicer, sliding the onion across the blade sideways (the narrow part facing forward). Be sure to use the finger guard to protect your fingers. If you don't have a mandolin, slice the onions thinly with a chef's knife.
Melt 3 tablespoons of butter over medium heat in an 6-quart enameled cast-iron pot (or another large heavy pot with a lid). Add the onions, sprinkle them with 2 teaspoons of salt, then cover and cook until the onions have heated through and started to steam, about 10 minutes.
Uncover the pot, stir in the black pepper, then reduce the heat to low and cook, stirring occasionally, until the onions have caramelized, about 3 hours.
Make the soup: When the onions have completely cooked down, (the liquid has evaporated, and the onions have turned amber), add the wine and raise heat to high. Cook until almost all liquid has evaporated, about 15 minutes.
Tie the thyme and bay leaves into a bundle (aka bouquet garni) with kitchen twine. Add the stock, water, and the bouquet garni to the pot with the onions. Bring to a boil (this can take about 15 minutes). Reduce to a simmer and cook, uncovered, until the soup has thickened, 20 to 30 minutes.
Remove the pot from heat, remove the bouquet garni, and whisk in the remaining 2 tablespoons of butter. Taste and adjust the seasoning as needed. If desired, you can add ½ to 1 teaspoon of sugar if the soup isn’t sweet enough for you.
Prepare the bread slices: Cut two ½-inch slices of the baguette for every serving of soup (make sure they will fit in the ramekins). Lightly toast the slices in the toaster until they are crisp and dry but not browned. Alternatively, preheat the oven broiler and place the bread slices on a half sheet baking pan. Broil until the slices, about 1 minute per side.
Rub one side of each toast with the garlic clove and set aside.
Assemble the soup: Add ½ teaspoon of sherry (if using) to the bottom of four 16-ounce oven-safe ramekins, then ladle the soup on top. Top each serving of soup with the two garlic-rubbed toasts. Divide the cheese among the servings, covering the bread and some of the soup.
Carefully broil the tops of the soup with a chef's torch until cheese is melted and bubbling, or place the ramekins on the half sheet baking pan and transfer to oven to broil and melt the cheese, about 4 to 8 minutes. See the Recipe Notes for finishing the soup in non-oven-safe soup bowls.
Serve and enjoy your afternoon's labors!
Storage instructions: French onion soup can be made up to 3 days ahead (without toast and cheese) when cooled and refrigerated, or up to 6 months ahead if frozen.
Make-ahead instructions: Caramelized onions can stored in an airtight container in the fridge for a week or more. You can also freeze them for up to two months. The toasts can be made (without cheese) and kept sealed at room temperature for up to 3 days.
Notes
You can also use 3 tablespoons of ghee (clarified butter), a butter substitute or olive oil for cooking the onions. Ghee has a higher smoke point than butter, so it's less lightly to burn while the onions are cooking down.You can make French Onion Soup without the white wine - just replace it with more beef stock to deglaze the pan (to loosen up the brown bits from the pan), then adjust the taste of the soup later with a bit lemon juice (to add acidity).Finishing the soup with sherry, cognac, or cointreau adds depth and a touch more sweetness to the soup, but since the alcohol isn't cooked off here, it's use is optional and for adults-only. Using sherry makes the soup not pregnancy- or kid-friendly.You can substitute grated Emmentaler, Gouda, Swiss, Fontina, or Mozzerella for the Gruyére if you'd prefer.If you don't have oven-safe ramekins, then top each garlic-rubbed toast with some cheese and melt in the broiler prior to putting them on the soup, about 2 minutes. Divide the sherry and soup among the bowls, sprinkle with the remaining cheese, and top each serving with two cheese toasts.