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Slow Cooker French Onion Soup Recipe

Slow Cooker French Onion Soup Recipe


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4.9 from 38 reviews

  • Total Time: 10 hours 15 minutes
  • Yield: 8 1x

Description

Hearty French onion soup blends rich, caramelized onions with savory beef broth and melted Gruyère cheese. Comforting layers of slow-cooked goodness invite you to savor each spoonful of this classic French culinary delight.


Ingredients

Scale

Main Ingredients:

  • 3 pounds sweet onions, thinly sliced
  • 6 cups beef stock
  • 1 French baguette, sliced
  • 1 cup shredded Gruyere cheese
  • 1 cup shredded Asiago cheese

Seasoning and Herbs:

  • 3 tablespoons unsalted butter, melted
  • 2 teaspoons brown sugar
  • 6 sprigs fresh thyme
  • 1 bay leaf
  • Kosher salt, to taste
  • Freshly ground black pepper, to taste

Instructions

  1. Combine sliced onions with melted butter, brown sugar, and salt in the slow cooker. Nestle thyme sprigs and bay leaf on top. Set slow cooker to high for 8-10 hours, allowing onions to caramelize and develop rich, deep flavor.
  2. Occasionally stir onions if convenient, though not mandatory. Slow, consistent heat will transform raw onions into golden-brown delicacy.
  3. After caramelization, pour beef stock into the slow cooker. Season with salt and pepper. Stir thoroughly and continue cooking on high for 2-3 hours to enhance flavor complexity and allow ingredients to meld together.
  4. When soup nears completion, prepare baguette. Preheat broiler and toast bread slices for 1-2 minutes per side until crisp and golden brown. Monitor closely to prevent burning.
  5. Transfer soup into oven-safe ramekins. Top each serving with toasted baguette slices. Generously sprinkle Gruyère and Asiago cheeses over bread. Broil for approximately 2 minutes until cheese becomes bubbly and develops golden color.
  6. Remove broiled soup carefully. Allow brief cooling period. Serve immediately, enjoying the harmonious blend of caramelized onions, savory broth, and melted cheese.

Notes

  • Caramelize onions slowly to develop deep, rich flavor by cooking them on low heat for 8-10 hours, allowing natural sugars to break down and create a sweet, complex taste.
  • Use dark brown sugar to enhance the caramelization process, providing a deeper color and more intense sweetness to the onions.
  • Choose high-quality Gruyère and Asiago cheeses for authentic flavor, ensuring they’re freshly grated for maximum melting potential and richness.
  • Adapt the recipe for vegetarian diets by substituting beef stock with robust vegetable stock and adding extra umami through mushroom base or miso paste to maintain depth of flavor.
  • Prep Time: 15 minutes
  • Cook Time: 10 hours
  • Category: Dinner, Appetizer
  • Method: Slow Cooking
  • Cuisine: French

Nutrition

  • Serving Size: 8
  • Calories: 250
  • Sugar: 3g
  • Sodium: 800mg
  • Fat: 10g
  • Saturated Fat: 6g
  • Unsaturated Fat: 4g
  • Trans Fat: 0g
  • Carbohydrates: 30g
  • Fiber: 2g
  • Protein: 10g
  • Cholesterol: 30mg