Make the Pastry. Crumb together butter into the flour. Add sugar. Add optional lemon zest. Mix in the beaten egg. Wrap and place in fridge for 30 minutes.

Peel and roughly cut apple into pieces. Do not cook apple, just heat in a large pan. Add sugar to taste depending on the sweetness of apples, and lemon juice. When just hot, turn off heat and leave to cool. Next, put the cooled apple into a buttered dish, approx. 28cm wide (Grandma uses a 28cm glass flan dish for her apple pie). Add more sugar.

Roll out pastry and put on top only. Make a few holes in the top and sprinkle with a little sugar on top. Bake for 35-45 minutes in oven 180C / fan 160C. When baking, put something underneath in case it leaks.

Make the custard. Place the cream, milk and vanilla seeds or essence in a saucepan and bring slowly to the boil over a low heat. Beat the egg yolks, corn our and sugar together in a bowl. Gradually beat in the warm cream mixture until smooth, then return the mixture to the pan. Heat gently, stirring constantly until the mixture thickens to coat the back of a wooden spoon. Serve immediately.