Slow Cooker French Onion Soup

Directions

Step 1: Caramelize the Onions

Place the sliced onions in the slow cooker. Add melted butter, olive oil, salt, and pepper. Cover and cook on low for 10–12 hours, until the onions are soft, golden, and deeply caramelized.

Step 2: Add Broth and Thyme

Stir in the beef stock, balsamic vinegar, and fresh thyme leaves. Cover and cook on low for an additional 6–8 hours, allowing the flavors to meld. If desired, add brandy for an extra layer of depth. Season to taste with additional salt and pepper.

Step 3: Prepare for Serving

Preheat your oven to 350°F (180°C). Divide the soup into oven-safe bowls placed on a baking tray. Place a slice of toasted bread on top of each bowl and sprinkle generously with Gruyère cheese.

Step 4: Melt the Cheese

Bake the bowls in the preheated oven for 20–30 minutes until the cheese melts. For a bubbly, golden-brown finish, broil for an additional 2–3 minutes. Remove carefully, let cool briefly, and serve hot.

Tips & Variations

• Cheese Options: Substitute Gruyère with Swiss, Emmental, or a mix of mozzarella and cheddar for a different flavor profile.
• Vegetarian Version: Use vegetable stock instead of beef stock for a meat-free version.
• Herb Enhancements: Add a bay leaf during cooking or sprinkle chopped parsley before serving for added aroma.
• Quick Finish: If short on time, caramelize the onions on the stovetop first for 20–30 minutes, then finish in the slow cooker with stock.

Serving Suggestions