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A portion of french onion soup in a teal bowl with 2 slices of baguette covered with melted cheese.

Slow Cooker French Onion Soup

By: Deborah
This slow cooker french onion soup is slow-simmered to perfection, packed with sweet caramelised onions and rich broth, topped with cheesy toasts. A simple, hands-off twist on the classic French bistro dish!
PREP: 20 minutes
COOK: 6 hours 25 minutes
TOTAL: 6 hours 45 minutes
Course: Soup, Starter
Cuisine: French
Servings: 8 people
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Equipment

Ingredients

  • 1 kg (2.2 lb) onions finely sliced
  • 45 g (1.6 oz) butter
  • 30 g (1.1 oz) brown sugar (I use soft light brown)
  • 1.8 litre (7 ½ cups) beef stock (made with stock cubes or pots)
  • 1 tbsp Worcestershire sauce
  • 1 clove garlic crushed
  • 75 ml (⅓ cups) dry sherry (see Notes)
  • 4 sprigs fresh thyme, or 1 tsp dried thyme
  • 1 bay leaf
  • slices of French baguette or bloomer bread (they need to be thickly sliced!)
  • salt and freshly ground black pepper
  • 150 g (5.3 oz) gruyere or comte cheese grated

Instructions

  • In a large frying pan, cook the onions, butter and brown sugar over a medium to low heat for about 20 minutes until soft and caramelised.
  • Once golden, add to them to the slow cooker along with the remaining ingredients except the bread and cheese.
  • Cook on low for 6 to 8 hours (I find 6 hours is enough). Heat the grill to high about 5 minutes before the end of the soup cooking time.
  • Grill one side of each slice of bread until lightly golden. Remove and discard the bay leaf and thyme sprigs from the soup, check the seasoning and add, to taste. Ladle the soup into bowls and place bread on the soup (you might need to cut the slices of bread in halves depending on what kind you use), toasted side onto the soup, then top with grated cheese.   Place the bowls onto a baking tray and then grill for 2 to 3 minutes or until cheese is melted and browned.   Enjoy...with some extra oozy cheesy toast on the side...if you fancy!

Notes

  • Sherry substitutes - brandy, dry vermouth, port, madeira or marsala are all good substitutes if you don't have dry sherry.
  • This slow cooker french onion soup recipe is easily halved if you’re cooking for less people.
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Nutrition

Calories: 313kcal | Carbohydrates: 36g | Protein: 15g | Fat: 12g | Saturated Fat: 7g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 3g | Trans Fat: 0.2g | Cholesterol: 33mg | Sodium: 854mg | Potassium: 696mg | Fiber: 3g | Sugar: 13g | Vitamin A: 347IU | Vitamin C: 10mg | Calcium: 280mg | Iron: 2mg

Nutrition information is automatically calculated, so should only be used as an approximation.

KEYWORDS comfort food, freezable, french onion soup recipe, make ahead, slow cooker french onion soup recipe, winter warmer
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