Chop the butter into small pieces and add to the Thermomix bowl together with the flour, sugar salt and water.

Turn out onto a floured surface and quickly bring it together with your hands. It will look quite crumbly to being with but should come together easily. Divide into two and shape each half of the pastry into a flattened disc.

Wrap each disc in plastic wrap or place in an airtight plastic bag and chill in the fridge for 30 minutes to an hour.

Peel and core the apples and slice into even sized slices around ¼ inch thick. Place apple slices into a bowl and sprinkle with lemon juice to prevent them going brown.

Sprinkle the flour mixture over the apple slices and mix well until all the apple slices are well covered.

First pre-heat the oven to 190 C / 375 F and prepare your pie dish by greasing and flouring it.

Take one disc of pastry and use a rolling pin to roll it out on a floured surface, turning a quarter of a turn every couple of rolls to maintain the circular shape. You are aiming for it to be approximately 2 inches wider than your pie tin on all sides.

Carefully transfer the pastry to the pie dish and press it into the bottom and sides.

Next take the apples and pile them into the dish, creating a slight mound in the centre. It should be very full as the apples will reduce slightly as they cook.

Now roll out the second disc of pastry. Use a pizza cutter or pastry cutter to cut the pastry into 10 strips.

Take 5 of the strips and lay them evenly spaced across the top of the pie with the longer strips in the centre and the shorter once towards the edges. Now fold back strips 2 and 4 half way and lay a long strip of pastry across them in the centre of the pie. Keep folding back alternating strips on both sides and laying across the remaining strips of pastry until the lattice pattern is complete.

Tuck in any excess pie dough around the edges and pinch together. You can create a crimped edge too if you like.

Whisk together the egg and sugar and use a pastry brush to brush the egg wash over the pie crust.

Bake in the oven for 20 minutes and then lower the temperature to 180 C / 355 F for a further 45 minutes to an hour. The pie filling should be bubbling through the gaps in the pastry. Note: Keep an eye on the pie crust as it cooks. Once it has turned brown, take a piece of foil, shape it into a dome over an upside down bowl and lay it over the pie for the remaining of the cooking time to prevent it from overcooking.

Allow to cool for at least an hour before cutting and serving.