Knead the ingredients for the filo and when the dough doesn't stick to your hands, roll it out, dusting it with flour so that it doesn't stick.

Peel and boil the potatoes and pass them through the food mill to mash them. Then beat the eggs with the milk in a pan and add the mixture to the purée (minding to keep 1/2 cup of the mixture for later).

Next add 1/2 cup lukewarm water from the boiled potatoes to the purée, and then add the oil, the sugar, the flour and the salt. 

Oil a baking tray and place the filo so that it hangs over the sides of the baking tray. Pour in the filling and fold the edges of the filo inwards.  

Finally, pour the 1/2 cup of the egg and milk mixture that you have kept, over the top. 

Bake in medium oven for about an hour until the pie is golden brown.