Put the cheese in a bowl, beat in 3 egg yolks (use the forth one in something else), a level teaspoon of mustard, a good shake of Worcestershire sauce and hot pepper sauce, and season to taste. Toast the bread.
Preheat the oven to 450 degrees F.
Whip the 4 egg whites until they stand in stiff peaks. Add a spoonful or so to the cheese mixture then gently fold the rest of them into the bowl. Put the toasts into an ovenproof dish and pour the mixture over them.
Bake in the oven for 10 minutes until browned and risen. Serve at once with a salad or spinach on the side.
Recipe courtesy of Jennifer Paterson and Clarissa Dickson Wright