Melt the butter in a heavy-bottomed saucepan. Add the bread slices and fry for 3 to 4 minutes on each side, or until they are golden brown and crusty. Remove the slices from the pan and drain on kitchen towels.

Preheat the oven to moderate 180°C (Gas Mark 4, 350oF).

Arrange the bread slices in an ovenproof tureen or individual bowls and arrange a slice of cheese over each one. Pour over the stock and put the tureen or bowls into the oven. Cook for 10 minutes, or until the cheese has melted.

Remove from the oven and serve at once.