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–+ servings
Slow Cooker French Onion Soup

Cozy Slow Cooker French Onion Soup for Ultimate Comfort

This Slow Cooker French Onion Soup is the perfect comfort food, combining caramelized onions with savory beef stock and herbs for a gourmet dish made easy.
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Prep Time 20 minutes
Cook Time 10 hours
Total Time 10 hours 20 minutes
Servings: 6 bowls
Course: Soups
Cuisine: French
Calories: 380
Ingredients Equipment Method Nutrition Notes

Ingredients
  

For the Soup
  • 3 lbs Sweet Onions Yellow or white onions if needed
  • 4 Tbsp Unsalted Butter Can substitute with olive oil for dairy-free
  • 1 Tbsp Brown Sugar Optional for less sweet flavor
  • 1 Tbsp Kosher Salt Adjust to taste
  • 1 tsp Freshly Ground Black Pepper Use to taste
  • 6 sprigs Fresh Thyme Can substitute with 1 tsp dried thyme
  • 1 leaf Bay Leaf Remove before serving
  • 8 cups Beef Stock Unsalted or homemade for lower sodium
  • 1 Tbsp Sherry Vinegar Can substitute with white wine or apple cider vinegar
For Serving
  • 1 loaf French Baguette Any crusty bread works well
  • 1 cup Gruyère Cheese Can substitute with Swiss or fontina
  • ½ cup Asiago Cheese Feel free to use more Gruyère

Equipment

  • 6-quart slow cooker
  • Baking Sheet
  • Oven

Method
 

Step-by-Step Instructions
  1. Slice the sweet onions thinly and place them into a 6-quart slow cooker. Pour melted unsalted butter over the onions and sprinkle with brown sugar and kosher salt. Add fresh thyme sprigs and a bay leaf on top. Cook on high for 8-10 hours until onions are caramelized, stirring halfway.
  2. Remove the bay leaf and thyme. Pour in the beef stock and sherry vinegar, then season with freshly ground black pepper and adjust salt if needed. Stir and cover. Cook on high for an additional 2-3 hours until heated through.
  3. Preheat the oven to broil. Slice the French baguette and arrange on a baking sheet. Broil for 1-2 minutes on each side until golden brown.
  4. Ladle the soup into bowls, top with baguette slices and sprinkle with Gruyère and Asiago cheeses, letting them melt over the bread.
  5. Return the bowls to the oven and broil for about 2 minutes until bubbly and golden. Watch closely to prevent burning.

Nutrition

Serving: 1bowlCalories: 380kcalCarbohydrates: 36gProtein: 15gFat: 22gSaturated Fat: 12gPolyunsaturated Fat: 1gMonounsaturated Fat: 8gCholesterol: 61mgSodium: 850mgPotassium: 600mgFiber: 2gSugar: 5gVitamin A: 500IUVitamin C: 10mgCalcium: 300mgIron: 2mg

Notes

This soup freezes well without cheese or bread. Store separately to maintain texture.

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