Slow Cooker French Onion Soup
Let your slow cooker do the magic while you cozy up under a blanket. This French onion soup is rich, cheesy, and slow-cooked to savory, golden perfection.
Ingredients
- 3 tablespoons unsalted butter
- 3 pounds sweet onions thinly sliced
- 1 tablespoon brown sugar
- 2 cloves garlic minced
- 6 sprigs fresh thyme
- 2 bay leaves
- 8 cups beef stock or veggie stock
- 2 tablespoons sherry vinegar
- Kosher salt and black pepper to taste
- 1 French baguette sliced
- 2 cups shredded Gruyère cheese
- ½ cup grated asiago or Swiss cheese
Instructions
- 1. Add butter, sliced onions, brown sugar, and garlic to a 6-quart slow cooker. Stir to combine.
- 2. Top with thyme sprigs and bay leaves. Cover and cook on LOW for 8 hours, until onions are deeply caramelized.
- 3. Remove thyme and bay leaves. Stir in beef stock and sherry vinegar. Season with salt and pepper. Cover again and cook on LOW for another 2 hours.
- 4. Preheat the broiler. Place baguette slices on a baking sheet and toast for 1–2 minutes per side, until golden.
- 5. Ladle hot soup into oven-safe ramekins or bowls. Top with baguette slices and a generous amount of cheese.
- 6. Broil for 2–3 minutes, until cheese is melted and bubbling.
- 7. Serve immediately, with extra thyme if you’d like!
Notes
Use sweet onions like Vidalia for best caramelization.
Freeze the soup base only—add bread and cheese fresh when reheating.
Gruyère is traditional, but Swiss or provolone work too.
Don’t skip the broiling step—it’s what makes this soup truly special.