French Onion Soup

Method

1. 1

   Start the onions

   Melt the butter and oil in a large heavy-based pot over medium heat for 2 minutes, until the butter foams; add the onions, sugar and salt and stir to coat.

2. 2

   Caramelise the onions

   Cook for 10 minutes over medium heat, stirring every few minutes, then reduce to medium-low as they colour and cook for 50 to 70 minutes, stirring and scraping often, until deeply golden brown, very soft and jammy.

3. 3

   Add flour and wine

   Stir in the flour over medium heat for 1 minute, until no dry flour remains; pour in the wine and simmer for 3 minutes, scraping the base, until reduced by about half.

4. 4

   Simmer the soup

   Add the stock, whole thyme sprigs and bay leaves; bring to a simmer over medium-high heat for about 5 minutes, then simmer uncovered over low heat for 25 minutes, until fragrant and lightly thickened.

5. 5

   Season the soup

   Remove the thyme sprigs and bay leaves, then taste and season with freshly ground black pepper and extra salt as needed; the broth should taste savoury and balanced.

6. 6

   Toast the baguette

   Heat the grill to high for 5 minutes; grill the baguette slices on a tray for 1 to 2 minutes per side, until dry and golden at the edges.

7. 7

   Top the soup

   Heat the grill to high if needed; divide the soup among four ovenproof bowls on a sturdy tray, then top each bowl with two toast slices and 37 g grated Gruyère.

8. 8

   Grill the cheese

   Grill the bowls 10 to 15 cm from the element for 3 to 5 minutes, watching closely, until the cheese is melted, bubbling and browned in patches; rest for 2 minutes before serving.

Tips

• Once the onions begin to colour, lower the heat and judge them by their deep golden-brown colour and jammy texture rather than the clock; reduce the heat further if they catch.
• Add a splash of water if browned bits stick before the onions are ready, and scrape them up as they cook.
• Use ovenproof bowls and place them on a sturdy tray before filling; the bowls and soup will be very hot after grilling.

Swaps

• Replace the dry white wine with the same amount of dry cider.
• Replace Gruyère with Comté or another firm cheese that melts well.

Storing

Refrigerate soup without the toast or cheese in a covered container for up to 3 days. Reheat until steaming throughout, then add freshly toasted baguette and cheese and grill just before serving.