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Cozy Slow Cooker French Onion Soup Recipe with Easy Gruyère Toast

slow cooker french onion soup - featured image
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A comforting and hands-off French onion soup slow-cooked to caramelized perfection, topped with melty Gruyère cheese on toasted rustic bread.

Ingredients

Scale
  • 4 large yellow onions, thinly sliced
  • 3 tablespoons unsalted butter
  • 3 garlic cloves, minced
  • 6 cups beef broth (or vegetable broth for vegetarian)
  • ½ cup dry white wine (optional)
  • 1 teaspoon Dijon mustard
  • 3 fresh thyme sprigs
  • 1 bay leaf
  • Salt and freshly ground black pepper, to taste
  • 6 thick slices baguette or rustic sourdough
  • 2 cups shredded Gruyère cheese (about 8 ounces)

Instructions

  1. Thinly slice 4 large yellow onions evenly; chill beforehand to reduce tears if desired.
  2. In a large skillet over medium heat, melt 3 tablespoons unsalted butter. Add onions and sauté, stirring occasionally, for about 15 minutes until softened and golden.
  3. Add 3 minced garlic cloves and sauté for 1-2 minutes until fragrant but not browned.
  4. Transfer onions and garlic to slow cooker. Pour in 6 cups beef broth and ½ cup dry white wine if using. Stir in 1 teaspoon Dijon mustard, 3 thyme sprigs, and 1 bay leaf.
  5. Cover and cook on low for 6 to 8 hours until onions are deeply caramelized and soup is flavorful.
  6. About 15 minutes before serving, season with salt and freshly ground black pepper to taste. Remove thyme sprigs and bay leaf.
  7. Preheat oven broiler. Place 6 slices of baguette or sourdough on a baking sheet and toast lightly on one side.
  8. Flip slices and generously sprinkle about ⅓ cup shredded Gruyère cheese on the toasted side.
  9. Broil for 2-3 minutes until cheese bubbles and turns golden brown, watching closely to avoid burning.
  10. Ladle hot soup into oven-safe bowls, float a slice of Gruyère toast on top, and serve immediately.

Notes

For vegetarian version, substitute beef broth with mushroom broth. For gluten-free, use gluten-free bread. Avoid lifting slow cooker lid during cooking to maintain heat. Broil Gruyère toast just before serving for best texture. If soup tastes too sweet, add a splash of vinegar or lemon juice. To thicken broth, simmer uncovered on stove for 10 minutes.

Nutrition

Keywords: French onion soup, slow cooker soup, caramelized onions, Gruyère toast, comfort food, easy soup recipe, slow cooker French onion soup

Find it online: https://breezybake.com/cozy-slow-cooker-french-onion-soup-recipe-with-easy-gruy-e-re-toast/