Heat the oven to 180°C (~350°F) and lightly grease a medium baking pan or line it with parchment paper.
In a bowl, crumble the myzithra with a fork. Add the sugar and flour, then pour in the milk gradually, mixing until you have a smooth, creamy filling — thick but spreadable. Add lemon zest or vanilla if you like a light aromatic note.
Place one phyllo sheet in the pan, brush lightly with olive oil. Repeat with 3–4 more sheets, brushing each layer generously.
Spread the cheese mixture evenly over the layered phyllo.
Fold the remaining sheets over the filling, brushing each one with butter or oil. Tuck the edges neatly around the filling.
With a sharp knife, score the top gently into portions (without cutting through). Bake for about 25–30 minutes, until the top is golden and crisp.
Let it rest for a few minutes, then dust generously with icing sugar and cinnamon. Serve warm — ideally with a cup of strong Greek coffee.