French Onion Soup Gratin

Melt the butter in a large saucepan over a low-medium heat, add the onions, sugar, and a pinch of salt, and cook very slowly for 35–40 minutes, stirring occasionally, until deeply golden and caramelised.

Add the garlic, thyme, and bay leaf and cook for 1 minute, then pour in the white wine and bubble for 2 minutes.

Pour in the stock, bring to a gentle simmer, and cook for 10 minutes, then remove the thyme and bay leaf and season generously.

Ladle the soup into 4 ovenproof bowls and float a slice of baguette on top of each.

Pile the grated Gruyère onto each crouton and place under a hot grill for 3–4 minutes until bubbling and golden.

Serve immediately, taking care as the bowls will be very hot.