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French Onion Soup


Recipe Name:  French Onion Soup recipe with instructions for Aga range cookers

By: Antonia

Meal Type: Cake
Prep Time: 10 minutes

Cook time: 3 hours

Servings: 6


This classic bistro favourite owes is depth of flavour to long, slow cooking of the onions. No need to stand and stir though – let the simmering oven do all the hard work.

An authentic soup relies on really good quality stock for flavour – it is worth buying a fresh stock (or using homemade) rather than relying on stock cubes. 

You'll need...


  • 50g butter
  • 1 tbsp. olive oil
  • 1 kg. onions
  • 1 heaped tsp. light brown sugar
  • 2 cloves garlic
  • 1 tbsp. chopped fresh thyme leaves
  • 2 tbsp. plain flour
  • 275ml. white wine
  • 1.2 l. good quality beef or vegetable stock
  • 1 tbsp. balsamic vinegar
  • salt and pepper
  • Worcestershire sauce, to taste (optional)
  • Half a baguette
  • 100g Gruyère or vegan cheese, finely grated
  • Equipment...


    1. Peel and slice the onions into thin slices. Heat the butter and oil in a large ovenproof pan or casserole on the simmering plate. Add the onions and cook gently for 5-10 minutes until starting to soften. Cover with the lid and transfer to the floor of the simmering oven. Cook the onions for 1.5-2 hours until they are very soft.

    2. Return to the simmering plate, remove the lid and cook for a further 5 minutes to drive off the liquid and further caramelise the onions. If your simmering plate is a little cool, you can do this on the boiling plate but watch carefully. The onions should turn a pale golden colour – be careful they don’t burn.

    3. Crush the garlic and add to the pan, along with the thyme leaves. Stir in the flour and cook for a couple of minutes. Add the wine, a little at a time, stirring after each addition. Bring to the boil and bubble for a few minutes to burn off the alcohol.

    4. Add the stock and vinegar and season well with salt and pepper. Bring back to the boil and transfer (without the lid) to the floor of the simmering oven for a further hour.

    5. When the soup is nearly done, prepare the cheesy toasts. Slice the baguette into 6 or 12 pieces (depending on thickness of baguette) and toast lightly on the simmering plate: cover the plate with a silicone liner and place slices directly on top. Lower the lid to toast, turning to toast the other side. Place toasts on a baking sheet and cover with the grated cheese. Slide onto the top runners of the roasting oven and ‘grill’ until the cheese had melted (2-4 minutes, checking regularly).

    6. Transfer the soup to the simmering plate and taste – adjust seasoning, adding a little Worcestershire sauce, if liked. Ladle into warm bowls and top with the cheesy toasts.

    Aga range cooker tips:

    • This soup takes a long time to cook but, other than slicing the onions, requires very little attention. The gentle heat from the simmering oven is ideal for the long, slow cooking of the onions. They may be sitting in quite a bit of liquid when you remove them from the oven but a quick blast on the top will drive off the liquid and they will quickly turn a light golden colour.
    • Although Aga range cookers don’t have a separate grill, the top of the roasting oven is extremely hot and works in the same way. If you have a Blake & Bull eCOOK or converted Aga range cooker then turn up the main oven 30degrees and then grill using the top of the lower oven. The element below the main ovens means the roof of the lower oven will be super hot and perfect for grilling!

    This fun family recipe has been scribed and tested by community member Antonia, who is a hard working mum with two boys. Her recipes are trialed in her much loved Aga range cooker and devoured by her family, allowing Antonia to provide accurate tips and advice on how to make the dishes a success! Go check her work out! She is a country girl, happily surrounded by an excitable Lab, her dear husband, two boys and the Cotswolds. 

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