Step 1

Add the butter and oil to a large Dutch oven or heavy-based saucepan. Heat over a medium-to-low heat.

Step 2

When the butter has just melted, add the sliced onions, salt and pepper.

Step 3

Cook, uncovered, for about 45-50 minutes, stirring occasionally at first, then often in the last 15-20 minutes (to stop the onions 'catching' on the bottom of the pan), until the onions are golden brown and caramelised. Be sure to keep a close eye on the onions, especially in the last 20 minutes, as you don't want them to burn at all. Turn down the heat a little if you're worried they'll burn.

Step 4

Add the garlic and cook for one minute, whilst stirring.

Step 5

Add the wine to 'deglaze' the pan and pick up all of those flavourful bits. Turn up the heat to medium-high and cook for about 5-8 minutes, stirring often until almost all of the liquid has evaporated and you can no longer smell the wine.

Step 6

Turn the heat back down to medium and stir in the flour. Cook for one minute, stirring constantly.

Step 7

Add the stock and Worcestershire sauce. Stir together, turn up the heat and bring to the boil.

Step 8

Turn the heat down to a simmer, stir again and place a lid on the pan. Simmer for 30 minutes. After 30 minutes, taste and add a little more slat if required (this wil depend on the saltiness of your stock).

Step 9

When the soup is nearly ready, start on the cheese baguette slices/croutons.

Step 10

Once the soup is ready, ladle out into grill(broiler)-safe bowls.

Step 11

Top each bowl with two of the baguette slices. Divide the grated Gruyere between the bowls, sprinkling it all over the soup and bread.

Step 12

Place the bowls on a tray under the grill (broiler) and slide under the heat.

Step 13

Grill for 2-4 minutes, until the cheese is melted and bubbling.

Step 14

Carefully remove the bowls (they'll be VERY hot) and serve sprinkled with fresh thyme leaves.

Step 15

Toast the baguette slices on both sides under the grill (broiler) until lightly browned.

Step 16

Once the baguette slices have been lightly browned under the grill (broiler), sprinkle them with the Gruyere and place back under the grill.

Step 17

Toast until the cheese is melted and bubbling.

Step 18

Ladle the soup out into bowls and place two slices of the cheese toasts on top of each bowl.

Step 19

Sprinkle with fresh thyme leaves and serve.