French onion soup

In a large flameproof casserole, melt the butter over a medium heat. Add the onions, stir to coat in the butter, then cook for 1½–2 hours, stirring frequently, until really brown and very soft, lowering the heat if they are catching. Add the flour and cook for 2 minutes, stirring. Meanwhile, tie the herbs together for convenience with cooking string, if liked.

Add the herbs, vinegar and stock to the casserole; season. Bring to the boil, then reduce to a gentle simmer and cook for 40 minutes. Stir through the Calvados, taste and add the sugar as needed to sweeten. Season, then remove and discard the herbs.

Preheat the grill to high. Cut the baguette into 2cm slices. Ladle the soup into ovenproof bowls, if you have them. Lay 2 slices of baguette on top of each bowl and sprinkle over a generous amount of cheese. Put the bowls in a roasting tin and grill for 3-5 minutes, or until the cheese has melted. If you do not have ovenproof bowls, arrange the bread slices in pairs on a foil-lined tray; cover each with cheese, grill until melted, then arrange on top of the soup. Scatter over the chives and serve straight away.