Onion Soup

Onion Soup

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French onion soup is a culinary classic that is hard to beat when it’s done right. Friends of mine at The Cartford Inn have their own version of this classic on the menu, but they are tight lipped on what makes theirs so good. With this as my inspiration, and a glut of onions in my kitchen I began to think how I could make my own version of this French classic on the grill.

The time-consuming part of making a classic French onion soup is caramelising the onion. My version treats the onions slightly differently, and by harnessing the power of the grill, you can keep the heat outside. If it’s a cooler day though, just keep that barbecue by the back door so you can pop out there as and when you need to keep an eye on things.


  • 1kg onions, skins on
  • 1 tbsp unsalted butter
  • 4 sprigs of fresh thyme
  • 2 tbsp plain flour
  • 175ml dry white wine
  • 750ml beef stock
  • salt and pepper
  • 1 tsp sugar (optional)
  • 8 slices, baguette, sliced 1cm thick
  • 200g blend of Lancashire, Comte and Emmental cheese, grated


  1. Setup your BBQ for 220c direct heat, with the lid down and vents open as applicable.
  2. Tumble the onions onto the grill over the direct heat and close the lid.
  3. Allow the onions to grill for 3-4 minutes before turning them and closing the lid. Repeat this until the onions skins are totally black all over, then remove from the grill and allow to cool slightly.
  4. With the onions cool enough to handle, carefully peel back the burnt outer skin to reveal the cooked, sweet flesh of the onion.
  5. Discard the burnt skins and roughly chop the cooked flesh.
  6. Heat the butter in a heavy gauge pan until foaming and add the thyme. Stir for a few seconds to awaken the herb and then add the cooked onion.
  7. Stir on a medium-high heat for 4-5 minutes to develop the thyme flavour within the onions.
  8. Sprinkle over the plain flour and stir through. Keep stirring with a wooden spoon and be sure the flour doesn’t stick and burn on the bottom of the pan. Stir for a minute or so to cook-out the flour before adding the white wine.
  9. Bring the wine to the boil and reduce by half. As the wine is reducing, use the spoon to scrape down the inside of the pan and return all the flavours to the soup.
  10. Once the wine has reduced, add the stock and bring to the boil. Simmer for 15 minutes, then season to taste with salt and pepper, and sugar if required.
  11. With the soup made, take it off the heat and allow to rest while you prepare the cheese croutons.
  12. Toast the slices of baguette over the direct heat of the grill – this really won’t take too long at all.
  13. Toast on both sides before topping each slice with the grated cheese mixture. Return the croutons to the barbecue this time in an area of indirect heat and close the lid. Bake for 6-8 minutes, depending on heat, until the cheese is bubbling, and remove.
  14. Serve the soup in warmed bowls and top with a cheesy crouton. Serve the remaining croutons on the side.

What I really like about this version of an Onion soup is how you are grilling and roasting the onions in the skins. The onion takes on a sweet smokiness as they sweat inside the outer layers, and the flesh is incredibly tender when you peel away that crispy blackened exterior. With so few ingredients it’s about making sure each step is not rushed, as time is the secret ingredient to developing a depth of flavour!

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