Preheat your oven to 180°C/350°F - place an oven tray in the oven and let this heat up too. When it comes to cooking your soufflés place them on this heated tray to ensure they maximise their exposure to heat, which will in turn, help them rise.
Prepare the moulds:.
Butter your moulds using upward strokes - this helps to guide your soufflé to the heavens. Then drop a spoonful of caster sugar into the mould, start tilting and turning the mould to ensure it's completely coated. Remove any excess sugar.
Prepare the custard:.
Place the milk, coffee and sugar into a small saucepan - stir to dissolve the sugar and let come to a near boil. Set to one side.
Place the butter in a saucepan over a gentle heat - allow to melt before adding the cornflour. Whisk until smooth before adding the milk mixture. Continue to whisk until thickened then remove from heat.
Allow to cool slightly before adding the egg yolks - it's most important to stir vigourously at this stage as you don't want to cook the eggs. You should have a thick glossy mixture.
Set this aside to cool.
Prepare the egg whites:.
Whisk the egg whites until soft peak forms then add the extra tablespoon of caster sugar - continue whisking until glossy.
Make the soufflé.
Place a quarter of the egg-white mixture into the cooled custard and stir well to slacken the mix. Add the remaining egg whites and gentle fold in trying to keep as much air in the mix as possible.
Spoon this into your moulds - filling about three-quarters full. Use your finger to create an indentation between the edge of the mould and the filling - this helps to concentrate the rise.
Place on the oven tray and cook for about 10 minutes - actually cooking time will depend on the size of the moulds used. Keep the oven light on so you can check on their progress without opening the door.