Fold each phyllo pastry sheet almost completely in half and arrange them in a suitable rectangular tray.
Sprinkle every 3rd sheet with crumbled feta cheese - do this until you've laid them all on. Cut the sheets in the tray into squares.
Pour warm melted butter along their cuts and edges. Beat the eggs with the salt using a whisk and add the milk. Pour this mixture over the sheets.
Using a knife, carefully fold the edges of the phyllo pastry inward a little and soak them with the milk mixture. Leave the phyllo pastry as is for 5-6 min., while shaking it periodically for the sheets to moisten better.
Put it in a cold oven, turn it up to 338°F (170 °C) with the fan on. Bake about 40 min. to a nice tan.
Eat while still warm, with yoghurt.