Slow-Cooker French Onion Soup


  • Prep Time30 mins
  • Total Time7 hrs 30 mins
  • Makes4 servings
Slow-Cooker French Onion Soup

(Photo: Roberto Caruso; prop styling: Catherine Doherty; Food styling: Michael Elliott)

Chatelaine Triple Tested

This is one of our favourite comfort foods, and preparing it in the slow cooker makes it that much easier. For a stovetop version, caramelize the onions and salt over medium until dark golden. Add flour, then vermouth, broth and water, and simmer, covered, for at least 30 min.


  • 1.75 kg cooking onions, thinly sliced (about 14 cups)

  • 3 tbsp butter, cubed

  • 1/4 tsp salt

  • 4 1/2 tsp all-purpose flour

  • 3 tbsp vermouth, or dry white wine

  • 900-mL carton beef broth

  • 1/3 cup water

  • 1 demi-baguette

  • 1 tbsp butter, at room temperature

  • 2 cups grated gruyere or emmental cheese


  • COMBINE onions with butter and salt in slow cooker insert. Season with fresh pepper. Cover and cook on high until onions are soft and dark brown, about 6 hours.

  • STIR in flour until well combined. Stir in vermouth. Scrape up brown bits from bottom. Add broth and water. Cover and continue cooking on high for 1 1/2 hours.

  • POSITION rack in top third of oven. Preheat broiler. Cut bread into 8 slices, each 1/2 in. thick. Butter both sides and place on a baking sheet. Broil until lightly golden, about 1 min per side.

  • ARRANGE 4 oven-safe soup bowls on a baking sheet. Ladle soup into bowls. Top each with 2 toasts. Sprinkle with cheese. Broil until cheese is bubbly, 2 to 4 min.

  • Make-ahead tip: Soup (without toasts) keeps well up to 3 days in the fridge or up to 2 months in the freezer. Flavour will improve as it sits.

Nutrition (per serving)

Calories 587, Protein 26g, Carbohydrates 56g, Fat 30g, Fibre 7g, Sodium 1840mg.
Excellent source of Vitamin B6.

Note: Our slow cooker recipes are developed with a 7 quart slow cooker.

Get more of our favourite slow cooker recipes.