Flavours of France: French onion soup

Bistro classics: Food writer Mary Cadogan reveals the history behind the flavoursome French broth

Onion soups can be traced back to Roman times when they were considered the food of the poor as onions were cheap and plentiful and the soup both filling and nutritious. The classic French onion soup with its topping of a cheesy croûte made it into a substantial meal that even the poorest could afford. Its full title is soupe à l’oignon Lyonnaise, and it is in the city of Lyon that it is thought the soup originated. The canuts or silk weavers worked long gruelling hours weaving the silk to make clothes for the rich. They had little time to cook and eat, so they concocted inexpensive dishes that would sustain them during their long working days. Go to Lyon today and the traditional Lyonnaise restaurants, called bouchons Lyonnais, will still serve hearty onion soups and other dishes, which are essentially peasant in origin, but have often been adapted and refined over time to appeal to more bourgeois tastes.

French onion soup made its way to the supper tables in England in the 1960s when food writer Elizabeth David introduced the cooking of France and the Mediterranean to our lack-lustre diets and changed our eating habits forever.

Onions are thought to have restorative powers and even today, all over France, this classic soup is often served to revellers in the early hours of New Year’s Day to keep the party going.

There is a curious custom in the south-west of France, where during a wedding party the happy couple will disappear to hide in a nearby house to spend their wedding night. After a time, the wedding guests would fill a bowl or chamber pot with onion soup and seek out the couple. The soup would have been doctored with excessive amounts of pepper, and when the couple were found, they were made to drink the concoction. The bride would have a fit of coughing and sneezing, but the groom would pronounce the soup to be delicious and would drink it down without flinching to demonstrate his strength and manliness. There is no such challenge in my version of this classic dish, and I hope you will enjoy every restorative mouthful.

French onion soup

If you want to get ahead, the soup can be made a couple of days in advance, or freeze it for up to a month, then reheat and top with the cheesy toasts. A good slug of Cognac can also be added with the wine to enrich the soup but this is optional.

Serves 4

1kg onions

2 tbsp olive oil

50g butter

1 tsp sugar

Large glass dry white wine

1.5 litres beef or chicken stock

Few thyme sprigs

2 bay leaves

4 thick slices of crusty bread

4 tsp wholegrain mustard

100g grated Gruyère or Beaufort cheese

Chopped parsley to finish

1 Peel and thinly slice the onions (use the slicer blade of a food processor if you have one). Heat the oil and butter in a large pan, add the onions and fry for about 5 minutes until the onions are starting to soften, then reduce the heat and stir in the sugar. Cook gently, stirring occasionally, for 30 mins until the onions are softened and golden.

2 Pour in the wine and allow to bubble until it has almost all evaporated, then pour in the stock, thyme, bay, salt and pepper. Bring to the boil, then simmer uncovered for 30 mins. Remove the thyme and bay leaves.

3 Toast the bread slices, then spread on one side with mustard and sprinkle with grated cheese. Toast until bubbling and golden. Divide the soup between four bowls and top with the cheesy toasts. Scatter with parsley and serve.