1. Preheat the oven to 375°F (190°C). Melt the butter in a saucepan over medium heat. Whisk in the flour and cook for 1 minute. Whisk in the milk and bring to a boil, whisking constantly, until thickened and smooth.

2. Remove the pan from the heat. Stir in the cheese and mustard and season with salt and pepper. Add the egg yolks into the cheese mixture one at a time, stirring until combined.

3. Beat the 5 egg whites until stiff peaks form. Stir about one fourth of the whites into the cheese mixture, then fold in the remainder.

4. Pour the mixture into a 6 cup soufflè dish. Sprinkle with the Parmesan. Place the dish on a baking sheet. Bake for 25–30 minutes, or until the soufflè is puffed and golden brown. Serve at once.

Variations

Mushroom Souffle:

Replace the cheese and mustard with 6oz (175g) very finely chopped mushrooms, cooked until tender with 1 finely chopped shallot in 1 tbsp butter. Drain the cooked mushrooms well, and stir in 2 tbsp chopped parsley.

Watercress Souffle:

Replace the cheese and mustard with ¾ cup loosely packed, chopped watercress leaves and 2 tsp finely chopped chives.

Carrot Souffle:

Replace the grated cheese and mustard with ½ cup boiled and purèed carrots and the grated zest of ½ orange.