Clean, wash and chop the leeks into pieces about 1/2″ (1 cm) thick.
Saute in half the oil and salt while stirring nonstop. Leave to cool, then mix with the crumbled feta cheese.
Cut the butter into small pieces and pour hot water over them. Add the rest of the oil and stir.
Lay out the phyllo pastry sheets and group them in pairs.
Smear one with the mixture of butter and oil, place the 2nd sheet on top and smear with mixture again.
Put some feta cheese mixture on top and wrap it into a roll. Do this for the rest of the sheets.
Arrange them in an oven dish some distance apart from one another, smear with oil and bake in a preheated 356°F (180 °C) oven until reddened.