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Slow-Cooker Lighter French Onion Soup

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A comforting, lighter take on classic French onion soup made in a slow cooker, featuring caramelized sweet onions and topped with toasty cheese croutons, perfect for busy weeknights.
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Prep Time 20 minutes
Cook Time 8 hours
Total Time 8 hours 20 minutes
Servings: 6 servings
Course: Main Course, Soup
Cuisine: French
Calories: 300
Ingredients Method Nutrition Notes

Ingredients
  

For the Soup
  • 6 tablespoons melted butter (or 4–5 tbsp butter + 1 tbsp olive oil) For a lighter fat profile
  • 4 large sweet onions, thinly sliced (Vidalia or Walla Walla, yellow onions work too) For caramelization
  • 2 small cloves garlic, minced
  • 1 heaping tablespoon brown sugar Helps speed up caramelization
  • 1/4 cup dry sherry Substitute with dry white wine or extra broth
  • 8 cups beef broth Use rich vegetable broth for vegetarian version
  • 4 sprigs fresh thyme Or 1 tsp dried thyme
  • 1 dried bay leaf
For Serving
  • 6 slices whole-wheat bread, cut to fit ramekins Substitute: sourdough or baguette
  • 6 oz shredded Jarlsberg Can use Gruyère or mozzarella for milder melt

Method
 

Preparation
  1. Add melted butter, thinly sliced onions, minced garlic, and brown sugar to the bottom of the slow cooker.
  2. Turn the slow cooker to HIGH. Stir occasionally. Let the onions caramelize for 60–75 minutes, until very soft and starting to turn golden.
  3. Pour in the dry sherry and scrape any browned bits from the slow-cooker sides.
  4. Add beef broth, fresh thyme sprigs, and the dried bay leaf. Stir to combine.
  5. Reduce the slow cooker to LOW and cook for 6–8 hours.
Serving
  1. When ready to serve, ladle the soup into six 1½-cup ramekins or oven-safe bowls.
  2. Cut bread into circles to fit the ramekins. Toast the bread until golden brown.
  3. Place one toasted bread circle on top of each ramekin of hot soup. Sprinkle about 1 tablespoon (or more to taste) of grated Jarlsberg over each bread round.
  4. Arrange ramekins on a baking sheet. Broil for 1–2 minutes until cheese is melted and bubbly—watch closely to prevent burning.
  5. Serve immediately.

Nutrition

Serving: 1gCalories: 300kcalCarbohydrates: 30gProtein: 10gFat: 15gSaturated Fat: 8gSodium: 800mgFiber: 4gSugar: 5g

Notes

For a more substantial meal, consider adding meatballs, or use this soup base with slow-cooker meatballs for another dinner twist. Store in the refrigerator for up to 3–4 days or freeze for up to 3 months.
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