Wash the dock, drain it from its water and cut it. Saute it in a little oil, then mix it with the crumbled feta cheese.
Butter the tray in which you will bake the pie. Arrange three sheets of phyllo pastry on top. Sprinkle butter on them and distribute some of the stuffing on top.
Repeat this process until you run out of the phyllo pastry sheets and filling. Then put the pie aside and prepare the topping.
Beat the eggs in a deep dish. To them add the milk, in which you've extinguished the baking soda. Sprinkle with a little salt.
Leave the resulting mixture to sit for 10 minutes and then pour it over the phyllo pastry sheets. Sprinkle the top with butter.
Bake the pie for about 40 minutes in a moderately heated oven.