Cover a greased and floured tray with a phyllo pastry sheet. Clean the leeks, cut them into small pieces and mix with the warm butter.
Season to taste with salt and black pepper. Beat the eggs with the sour cream and crumbled feta cheese. Arrange the salty cake by alternating phyllo pastry sheets with both of the mixtures.
Bake in a preheated 428°F (220 °C) oven for 25 minutes.