4.8 from 78 votes
Slow Cooker French Onion Soup
This slow cooker French onion soup features sweet caramelized onions cooked low and slow with butter and brown sugar, then simmered in beef stock with herbs. Topped with toasted baguette slices and melted gruyere and Asiago cheeses, it delivers a rich, hearty soup with deeply developed onion flavor.
Prep Time
15 mins
Cook Time
10 hrs 5 mins
Total Time
10 hrs 20 mins
Servings:
8
servings
Course:
Soup
Ingredients
- 3 pounds sweet onion thinly sliced
- 3 tablespoons butter melted, unsalted
- 2 teaspoons brown sugar
- salt to taste, Kosher salt and freshly ground
- black pepper to taste, Kosher salt and freshly ground
- 6 prigs thyme fresh
- 1 bay leaf
- 6 cups beef stock
- 2 teaspoons sherry vinegar
- 1 baguette sliced, French
- 1 cup gruyere cheese shredded
- 1 cup Asiago cheese shredded
Instructions
- Place onions into a 6-qt slow cooker.
- Stir in butter, brown sugar and 1 teaspoon salt; top with thyme and bay leaf. Cover and cook on high heat for 8-10 hours, or until onions are caramelized and browned.*
- Stir in beef stock and sherry; season with salt and pepper, to taste. Cover and cook on high heat for 2-3 hours, or until heated through. Remove and discard thyme and bay leaf.
- Preheat oven to broil.
- Place baguette slices onto a baking sheet. Place into oven and broil until golden brown on both sides, about 1-2 minutes per side; set aside.
- Divide soup into ramekins or ovenproof bowls. Place onto a baking sheet. Top with baguette slices to cover the surface of the soup completely; sprinkle with cheeses.
- Place into oven and broil until golden brown and cheeses have melted; about 2 minutes.
- Serve immediately.
Cup of Yum
Notes
- Stir the onions halfway through cooking to prevent them from sticking or burning.
- Use ovenproof bowls for mounting bread and cheese to broil safely.
- Broil the soup briefly just until the cheese is melted and golden, watch closely to avoid burning.