Method

1. Preheat the oven to 180⁰C / 350⁰F / Gas Mark 4
2. Cream the butter until it is soft then beat in the sugar until they are fluffy and light in color
3. Beat the egg and add to mixture, beating it in well
4. Sieve the flour 
5. Peel, core and roughly chop the apple
6. Stir flour and apple into other ingredients with the milk
7. Line a swiss roll tin with baking parchment
8. Turn into the swiss roll tin and spread it evenly to the sides
9. Bake in the preheated oven for 25 to 30 minutes until cake is golden brown and springy to touch
10. Sprinkle sparingly with sugar and leave to cool
11. Cut into squares when cooled