French onion soup with cheesy croutons

Melt 80g butter in a large, heavy-based pan over a low heat. Add the onions with a pinch of salt. Cook, stirring regularly, for 1½-2 hours, until a deep, golden brown.

When caramelised, stir in the flour and thyme leaves; cook for 1-2 minutes, stirring, then add the vinegar and about ¹⁄ ³ of the cider, stirring. Whisk in the rest of the cider and the stocks, then bring to the boil. Turn the heat down and simmer for 1 hour.

Meanwhile, to make the croutons, preheat the grill to high. Rub both sides of the baguette slices with the garlic, then brush one side with the melted butter and grill on that side. Turn over, then scatter the other side with the grated cheese and grill until melted and golden. Season the soup, if needed, then divide between 4 bowls. Place 2 toasts on the top of each bowl, scatter over the chives and serve straight away.