Melt butter in saucepan, add flour and cook 1 minute over low heat. Add hot milk and stir constantly over low heat with spoon or whisk until smooth and thick.
4
Allow to cool slightly. Beat egg yolks with sugar and vanilla and mix well into sauce.
5
Beat egg whites until they are stiff but not dry, fold into sauce mixture gently without losing aeration.
6
Pour the mixture into a buttered and lightly sugared 1.5 litre souffle dish (or individual dishes if you prefer), bake in preheated oven at 180C/350F for 30-40 minutes until well risen and golden.