Description
A hands-off slow cooker French onion soup recipe that delivers deep caramelized onion flavor and a gooey Gruyère cheese topping, perfect for cozy comfort food.
Ingredients
Scale
- 4 large yellow onions, thinly sliced
- 4 tablespoons unsalted butter
- 1 tablespoon olive oil
- 6 cups (1.4 liters) low-sodium beef broth
- ½ cup (120 ml) dry white wine (optional, can substitute with extra broth or apple cider vinegar)
- 1 tablespoon balsamic vinegar
- 3 garlic cloves, minced
- 3–4 sprigs fresh thyme or 1 teaspoon dried thyme
- 1 bay leaf
- Salt and black pepper, to taste
- 1 loaf baguette (day-old or slightly stale)
- 2 cups shredded Gruyère cheese (about 200g)
Instructions
- Heat butter and olive oil in a large skillet over medium-low heat. Add thinly sliced onions and a pinch of salt. Stir occasionally and cook slowly for 30-40 minutes until onions are soft and deep golden brown.
- Add minced garlic and cook for 1 minute until fragrant. Pour in white wine or extra broth to deglaze the pan, scraping up browned bits. Simmer for 2 minutes to reduce slightly.
- Transfer the onion mixture to the crockpot. Add beef broth, balsamic vinegar, thyme sprigs, and bay leaf. Stir gently to combine.
- Cover and slow cook for 6-8 hours on low or 3-4 hours on high until flavors meld and soup is rich. Taste and adjust salt and pepper near the end of cooking.
- About 15 minutes before the soup finishes, preheat the oven broiler. Slice baguette into ½-inch thick rounds and toast lightly on a baking sheet. Shred Gruyère cheese.
- Ladle hot soup into oven-safe bowls. Top each bowl with 2-3 baguette slices and a generous handful of Gruyère cheese. Place bowls on a baking sheet and broil 8-10 minutes until cheese is bubbly and golden brown. Watch closely to avoid burning.
- Carefully remove from oven and serve immediately.
Notes
Caramelize onions low and slow to avoid burning and achieve deep sweetness. Use fresh thyme if possible and tie sprigs for easy removal. Watch cheese carefully under broiler to prevent burning. For vegetarian version, substitute beef broth with vegetable broth and add soy sauce or tamari for umami. Leftover soup (without bread and cheese) stores well in fridge up to 4 days or freezes up to 3 months.
- Prep Time: 15 minutes
- Cook Time: 6-8 hours
- Category: Main Course
- Cuisine: French
Nutrition
- Serving Size: 1 bowl (about 1.5 cu
- Calories: 280
- Sodium: 600
- Fat: 14
- Carbohydrates: 28
- Fiber: 3
- Protein: 12
Keywords: French onion soup, crockpot recipe, slow cooker soup, comfort food, caramelized onions, Gruyère cheese, easy soup recipe