French Onion Soup Recipe
Beef Broth + Caramelized Onions + Parmesan Crouton + Swiss Cheese
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Ingredients
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Soup Base
Croutons & Cheese
Method
Soup Base
Heat fat
In a large, heavy-bottomed pot or Dutch oven, melt 2 tbs unsalted butter with 1 tbs olive oil over medium heat until the butter foams.
Caramelize onions
Add all sliced onions, 1 tsp kosher salt, and 1 tsp granulated sugar to the pot. Stir to coat. Cook over medium-low to medium heat, stirring every 2–4 minutes to prevent sticking, adjusting heat as needed. Continue cooking until onions are deeply golden brown and caramelized, about 40–50 minutes. Scrape browned bits from the bottom occasionally.
Deglaze
Raise heat to medium-high. Sprinkle 2 tbs flour over the onions and stir for 1–2 minutes to cook the raw flour taste and absorb juices. Pour in 1 cup dry white wine, scraping up any browned fond from the pot, and simmer 2–3 minutes until the wine has mostly reduced.
Simmer the soup
Add 6 cups beef broth, 1 tbs beef demi-glace (if using), 3 sprigs fresh thyme, 2 bay leaves, and 1 tsp Worcestershire sauce. Bring to a gentle simmer, then reduce heat to low and simmer, uncovered, for 20–30 minutes to meld flavors. Taste and adjust seasoning with additional salt and pepper as needed. Remove thyme sprigs and bay leaves before serving.
Croutons & Cheese
Toast baguette slices
Preheat oven broiler (or oven to 400°F / 200°C). Brush both sides of baguette slices lightly with 1 tsp olive oil and place on a baking sheet. Toast under broiler or in oven until lightly golden, about 1–2 minutes per side under broiler or 6–8 minutes at 400°F, flipping once. Keep an eye so they don’t burn.
Assemble croutons
Combine 2 cups grated Gruyère and 1 cup grated Parmesan in a bowl. Place toasted baguette slices on a baking sheet, sprinkle each slice with a generous layer of the cheese mixture (about 2–3 tbs cheese per slice). Grind a little black pepper (about 1/8–1/4 tsp across all slices) over the cheese.
Melt cheese
When the soup is ready and still hot, ladle soup into ovenproof bowls or crocks, distributing onions and broth evenly. Float 1–2 cheese-topped baguette slices on each bowl. Place bowls on a baking sheet and broil in the oven until the cheese is bubbly and golden brown, about 2–4 minutes. Alternatively, melt cheese under a torch if available.
Serve
Carefully remove hot bowls from oven. Let rest 1–2 minutes, then serve immediately with additional grated Parmesan at the table if desired.