Preheat the oven at 180° C.
In a bowl, crush the Feta, Anari and add the Halloumi, eggs, mint, baking powder and black pepper.
Stir well.
Spread the base of a rectangular pan with dimensions 22x30cm with butter. Spread 4 Filo dough leaves, sprinkling them with butter. Add the mixture on top and spread evenly with a spoon.
Fold the protruded leaves towards the inside, sprinkling them with some butter. Shrivel the rest 6 leaves one by one and place them on top of the mixture. Sprinkle the leaves with the rest of the butter and cook in the preheated oven for 40 minutes or until the cheese pie becomes golden-brown. Set aside for a bit to cool down, cut in pieces and serve.