Roasted Red Onion Soup with Welsh Rarebit Toasts

Being a child of the seventies and eighties, I’m a natural sucker for a French onion soup. The thrill of seeing molten cheese on a floating toast was (and still is) my idea of heaven, married with the umami rich depth of the ‘oniony’ broth it was unlike anything I had ever tasted before – it was Wales in the seventies after all! French Onion Soup was one of the first things my husband and I attempted for our first dinner party when we were young out of work actors living in a tiny flat in South London, oh the sophistication.

It was with memories of this that I thought I decided to try a riff on the classic. I wanted to try roasting red onions and to update the usual melting gruyere with another part of my history – Welsh rarebit. Rarebit is really just an elaborate cheese on toast with many recipe variations if you care to search the internet, but this is one that I grew up with in Cardiff and the one that we still serve at our restaurant Gastrono-me in Suffolk today.

By using red onions and red wine the soup becomes more intense in flavour and colour, and I think embodies autumn’s rich hues perfectly.

Roasted Red Onion Soup with Welsh Rarebit Toasts

Recipe by Gemma SimmoniteCourse: MainDifficulty: Medium


Prep time


Cooking time




  • 750g red onions sliced

  • 4 tbsp of olive oil

  • 30g butter

  • 1 large glass of red wine

  • 1 tsp of dark soy sauce

  • 1tbsp of balsamic vinegar

  • 2 tsp of sugar

  • 2 sprigs of thyme

  • 1 bay leaf

  • 1-2 cloves of garlic minced

  • 1 litre of vegetable stock

  • Salt and ground black pepper

  • ½ French stick for rarebit toasts

  • Welsh Rarebit Mix
  • 200g of extra mature Cheddar cheese, grated

  • 3 tbsp of milk

  • 1 tsp of English mustard

  • 1/2tsp of white pepper

  • Salt to taste

  • 2 egg yolks


  • Preheat the oven to 230C/450F/gas mark 8
  • Put the onions in a large ovenproof crockpot, pour over the olive oil and roast for 25mins or until the onions have softened and begun to char at the ends slightly
  • Remove from the oven, and transfer to a medium heat on the hob.
  • Add the butter, red wine, soy sauce, balsamic vinegar, sugar, thyme and bay leaf and minced garlic
  • Stir constantly until jammy and caramelised
  • Pour in the vegetable stock, and season to taste, cook for a further 15 mins
  • Meanwhile make the rarebit mix. Add the cheddar, mustard, salt and pepper to a bowl and beat well. Add the egg yolks one at a time, with a little of the milk and beat well after each addition. Continue until you have a golden well incorporated mix.
  • When ready to serve, cut the bread into 6 rounds and toast lightly under a hot grill
  • Dollop on the rarebit mix and grill until the toasts are puffy and bubbling hot
  • Pour the warmed soup into bowls, and top with the melting cheesy rarebit toast


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