Classic Crockpot French Onion Soup (Print version)

A cozy slow cooker French onion soup with deeply browned onions, savory broth, toasted baguette, and bubbling Gruyere.

# Ingredients:

For the soup

01 - 5 large yellow onions, thinly sliced, about 3 lb (1.4 kg)
02 - 4 tablespoons (56 g) unsalted butter
03 - 1 tablespoon olive oil
04 - 1 teaspoon kosher salt, plus more to taste
05 - 1/2 teaspoon black pepper
06 - 1 teaspoon sugar, optional
07 - 3 cloves garlic, minced
08 - 2 tablespoons all-purpose flour
09 - 1/2 cup (120 ml) dry sherry or dry white wine
10 - 8 cups (1.9 L) low-sodium beef broth
11 - 1 tablespoon Worcestershire sauce
12 - 4 fresh thyme sprigs or 1 teaspoon dried thyme
13 - 1 bay leaf

For serving

14 - 12 slices baguette, cut 1/2 inch thick
15 - 1 tablespoon olive oil for brushing
16 - 2 cups (225 g) shredded Gruyere cheese
17 - 1/4 cup (25 g) grated parmesan cheese

# Instructions:

01 - Melt the butter with 1 tablespoon olive oil in a wide skillet over medium heat. Add onions, salt, pepper, and sugar if using. Cook for 25-35 minutes, stirring often, until the onions are soft, jammy, and deep golden.
02 - Stir in the garlic and cook for 30 seconds. Sprinkle the flour over the onions and stir for 1 minute to coat them evenly.
03 - Pour in the sherry and scrape up the browned bits from the bottom of the skillet. Let it bubble for 1 minute, then transfer everything to a 5 to 6 quart slow cooker.
04 - Add the beef broth, Worcestershire sauce, thyme, and bay leaf. Cover and cook on low for 4-5 hours or high for 2-3 hours. Remove the thyme stems and bay leaf, then taste and adjust salt.
05 - Place baguette slices on a sheet pan and brush lightly with olive oil. Broil for 1-2 minutes per side until crisp and golden.
06 - Ladle soup into oven-safe bowls set on a sheet pan. Top each bowl with 2 baguette slices, Gruyere, and parmesan. Broil for 2-4 minutes until the cheese is melted, bubbly, and browned in spots.

# Good to know:

01 - A 5 to 6 quart slow cooker gives the onions and broth enough room.
02 - For the deepest flavor, brown the onions in a skillet before slow cooking.
03 - Serve right after broiling so the cheese stays stretchy and the bread stays crisp.

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