1. Toast the bread. Boil the cider and shallots in a small saucepan over medium heat until the cider is almost completely evaporated. Transfer to a small bowl.

2. Wipe out the saucepan. Add the butter and melt over medium-low heat. Whisk in the flour and let bubble without browning for 1 minute. Whisk in the milk. Cook, whisking often, until simmering and thickened. Add the Stilton and Cheddar cheeses and whisk until melted. Remove from the heat and whisk in the egg yolks, mustard, and shallots. Spread the cheese mixture generously on to each toasted bread slice.

3. Position a broiler rack about 6 in (15cm) from the source of heat and preheat the broiler. Arrange the toasts on a broiler pan and broil for 1-2 minutes, until the tops are golden and bubbling.

4. Toss the watercress, pears, walnuts, oil, and vinegar, in a bowl, and season with pepper. Divide among serving plates. Place the toasts on the side and serve at once.