1 Place the flour in a pile on the work surface and stir in the sugar and a pinch of salt. Create a well in the middle and place the butter around the well. Crack the egg into the well and chop all the ingredients up together so that breadcrumbs are formed. Knead together until a smooth dough is formed. Shape into a ball, wrap in plastic wrap and chill for 30 minutes.
2 Using a 20cm Tatin dish or shallow cast iron oven proof frying pan, sprinkle over a generous layer of sugar (approx. 100 g). Add 50g of the butter and place the apples on top.
3 Heat the dish on the hob on a medium heat for around 15 minutes. Remove from the heat when the sugar begins to caramelize. Leave to cool, then add the remaining sugar and the butter.
4 Heat the oven to 200°C (180° fan) 400°F gas 6.
5 Roll out the pastry on a floured work surface, place on top of the apples and push the edges down into the dish. Bake for around 30 minutes. Remove from the oven, leave to cool for 10 minutes then, very carefully, invert onto a serving plate and serve warm.