French Onion Soup (Soupe à l'Oignon Gratinée)

Method

Tap a step when it's done.

1. 1Melt the butter with the olive oil in a large, heavy pot over medium heat. Add the onions, cover and cook for 15 minutes until soft and releasing their juices.
2. 2Uncover, add the sugar and salt and lower the heat to medium-low. Cook for 40-50 minutes, stirring every 5 minutes and scraping the bottom, until the onions are deep brown and jammy.
3. 3Add the garlic and stir for 1 minute. Sprinkle in the flour and cook for 2 minutes, stirring it into the onions.
4. 4Add the vinegar and scrape the bottom of the pot, then gradually stir in the hot stock. Add the thyme, bay leaf and pepper and simmer gently for 25-30 minutes; check the salt.
5. 5Meanwhile, heat the oven to 200 °C and toast the baguette slices on a tray for 8-10 minutes, until dry and lightly golden on both sides.
6. 6Switch the oven to the grill (broiler) setting. Remove the herbs, ladle the soup into ovenproof bowls and top each with 2 toasts and a generous handful of cheese.
7. 7Set the bowls on a tray on the top rack and grill for 4-6 minutes, watching closely, until the cheese is melted and blistered brown in spots. Serve immediately.