• Melt the butter in a saucepan. Stir in the flour and cook for 1 to 2 minutes, stirring constantly.
• Remove from the heat and gradually add the hot milk, stirring vigorously. When all the milk is incorporated, return to the heat and bring slowly to the boil, stirring constantly.
• Simmer gently until the sauce thickens. Lower the heat, stir in the grated cheese, mustard, and salt and pepper to taste.
• Remove from the heat and allow to cool slightly. When cool, beat in the egg yolks.
• Whisk the egg whites in a clean bowl until stiff. Fold 1 tbsp of the egg whites into the cooled sauce with a metal spoon, then fold in the remainder, making a figure of eight pattern with the spoon and bringing the sauce up from the bottom of pan with the spoon.
• Spoon the mixture lightly into the prepared souffle dish and bake in the oven preheated to fairly hot (190°C/3 75°F or Gas Mark 5) for 30 to 35 minutes or until set and golden-brown. Serve immediately.

Souffles

• Souffles make ideal lunch dishes as they should be quickly made and quickly eaten. Many cooks are wary of making souffles as they are commonly thought of as being difficult, but this is not so if a few basic rules are followed and the cook keeps a cool head.
• Whisk the egg whites (see recipe) until very stiff and standing in peaks (turn the bowl upside down - if the egg whites do not drop, then they are stiff enough). Fold 1 tbsp/1 tablespoon of egg white into the sauce before folding in the bulk. This helps to soften the sauce.
• Preheat the oven to the required temperature with the baking sheet on the centre shelf of the oven - this ensures that when the souffle is put on the baking sheet in the hot oven, it will start cooking immediately. Remove shelves above the centre shelf to allow room to rise.
• Time the cooking of the souffle accurately, and be prepared to serve and eat immediately the souffle is ready.