This Slow Cooker French Onion Soup is the kind of recipe that feels cozy from the very first spoonful. Sweet, caramelized onions slowly simmer into a rich, savory broth, filling your kitchen with that classic French bistro aroma. It’s mostly hands-off, deeply comforting, and perfect for chilly evenings when you want something simple but special.
Ingredients :
For the Soup:
• Kosher salt and freshly ground black pepper, to taste
• 3 pounds sweet onions, thinly sliced
• 4 tablespoons unsalted butter, melted
• 2 teaspoons brown sugar
• 2 teaspoons sherry vinegar
• 1 tablespoon Worcestershire sauce
• 5 fresh thyme sprigs
• 3 bay leaves
• 6 cups beef stock
For Serving:
• 1 (12-ounce) French baguette, sliced
• 2 cups Gruyère cheese, shredded
Directions :
Step 1: Build the Onion Base
Add the thinly sliced onions to a 6-quart slow cooker. Pour in the melted butter, brown sugar, 1 teaspoon salt, sherry vinegar, and Worcestershire sauce. Stir gently until everything is coated.
Step 2: Let the Slow Cooker Work Its Magic
Cover and cook:
On High: 8–9 hours
On Low: 12–14 hours
Stir halfway through if possible to ensure even browning. The onions should be deeply caramelized, soft, and richly colored.
Step 3: Add the Broth and Herbs
Stir in the beef stock. Season with salt and pepper to taste. Add thyme sprigs and bay leaves. Cover and cook:
High: 2–3 hours
Low: 4–5 hours
Discard thyme and bay leaves before serving.
Step 4: Toast the Bread
Preheat the oven to broil. Arrange baguette slices on a baking sheet and broil until golden on both sides, about 1–2 minutes per side.
Step 5: Assemble the Soup
Ladle soup into oven-safe bowls. Place bowls on a baking sheet. Top each with toasted baguette slices, fully covering the surface. Sprinkle generously with shredded Gruyère.