Skip to content
Slow-cooker French onion soup recipe

Slow-cooker French onion soup recipe

44 ratings

Make the most of slow-cooker season! This French onion soup is so easy to make; simply bung in all your ingredients and let the slow-cooker do the work. See method

  • Serves 4
  • 4 hrs 00 mins
  • 386 calories / serving
  • Freezable


  • 800g thinly sliced onions
  • 50g unsalted butter
  • 2 tbsp caster sugar
  • 10g thyme sprigs
  • 1 bay leaf​
  • 1 tbsp plain flour
  • 1.4ltrs beef stock (made with 2 stock cubes)
  • 2 tbsp balsamic vinegar
  • 3 tbsp Worcestershire sauce
  • ¼ white baton
  • 75g finely grated Cheddar
If you don't have any Cheddar, try using another hard cheese

Each serving contains

  • Energy

  • Fat

    18g 26%
  • Saturates

    11g 57%
  • Sugars

    25g 28%
  • Salt

    2.9g 48%

of the reference intake
Carbohydrate 42.3g Protein 9.8g Fibre 5.5g


  1. Preheat a 2ltr (or larger) slow-cooker for 5 mins. Add 800g thinly sliced onions, 50g unsalted butter, 2 tbsp caster sugar, 10g thyme sprigs and a bay leaf; stir, then cover and cook on high for 3 hrs (stirring every 1 hr, if possible) until the onions are soft and golden.
  2. Stir in 1 tbsp plain flour, then pour in 1.4ltrs beef stock (made with 2 stock cubes), 2 tbsp balsamic vinegar and 3 tbsp Worcestershire sauce. Cover and cook for a further 1 hr.
  3. Preheat the grill to high. Cut ¼ white baton into 4 thin slices and grill on a foil-lined rack on both sides until golden. Divide 75g finely grated Cheddar between the toasts, then grill again for 30 secs-1 min until golden and bubbling. Ladle the soup into warm serving bowls and top each with a warm cheese crouton.

Tip: Make this vegetarian by swapping in vegetable stock and using 1-2 tbsp soy sauce instead of Worcestershire sauce.

Tip: Keep in an airtight container in the fridge for up to 3 days, or freeze for up to 1 month.

Freezing and defrosting guidelines

In order to enjoy optimum flavour and quality, frozen items are best used within 3 months of their freezing date. For more tips on freezing and defrosting food, read our article Love Your Freezer.

See more Soup recipes

You may also like

Be the first to comment

Before you comment please read our community guidelines.