Preheat the oven to 180 C / Gas 4. Grease four ramekin dishes.
In a clean mixing bowl, whisk the egg whites until stiff peaks form. In a separate bowl, whisk the egg yolks and sugar until pale and creamy.
In a saucepan over a medium heat, warm the milk then add flour, cornflour and cream and whisk constantly until thickened. Add the lemon zest and juice gradually, whilst whisking. Once thickened, remove from the heat. Whisk in the egg yolks. Allow to cool for 30 minutes.
Once cooled to room temperature, fold in the egg whites gently trying to keep the mixture as light as possible. Divide the mixture equally between the prepared ramekin dishes.
Bake in the preheated oven for 25 minutes until risen and golden. Do not open the oven door during cooking. Remove and dust with grated chocolate, if using, and icing sugar. Serve immediately.