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+ servings

Slow Cooker French Onion Soup

Prep Time20 mins
Cook Time6 hrs
Course: Appetizer, Dinner, Lunch
Servings: 8
Calories: 205kcal


  • slow cooker


  • 4 Tbsps butter
  • 6-8 large yellow onions, sliced
  • 3 cloves garlic, minced
  • 3 Tbsps flour
  • 1 Tbsp Worcestershire sauce
  • 1 tsp sugar
  • 2 32 oz cartons low-sodium beef broth
  • 1 oz pkg Au Jus seasoning mix
  • 1 loaf French bread, cut into 1-inch thick slices
  • Swiss cheese slices


  • In a large skillet, melt butter; add sliced onions. Sauté until onions are translucent and start to caramelize; add garlic.
  • Transfer onion mixture to slow cooker.
  • Mix together flour, Worcestershire, sugar, 1 teaspoon salt and 1/4 teaspoon pepper.
  • Pour broth, Au Jus mix and Worcestershire mixture into slow cooker, stirring to remove any lumps from the flour.
  • Cover and cook on low 4-6 hours.
  • Pour soup into oven-proof bowls. Place on a baking sheet, and put a piece of sliced bread on top of soup. Cover with cheese, and broil in oven 2-3 minutes, until cheese is bubbly.


Calories: 205kcal