Rinse the spinach thoroughly with water, clean it, and boil it together with the leeks, onions, and mint, all finely chopped. Once cooked, drain well and transfer to a large bowl.

Add the cheeses, evaporated milk, eggs, olive oil, and black pepper. Grease a baking pan with olive oil and lay down the phyllo sheets. Brush each sheet with olive oil before placing it in the pan. Use half the sheets for the bottom, then add the filling, and cover with the remaining sheets, brushing each with olive oil as you go.