In a large bowl, mix the feta, cream cheese, ricotta, Parmesan and eggs until well combined but slightly lumpy.

Place the phyllo dough on a large cutting board or flat surface and keep covered with a damp paper towel while working.

Preheat oven to 350 degrees. Lightly grease two large baking sheets.

Carefully remove one sheet of dough from the stack and place it in front of you vertically. Using a pastry brush, gently butter the surface of the phyllo sheet.

Drop a tablespoon of filling in the center of the sheet, about 2 inches up from the bottom edge. Fold the bottom edge up to cover the filling.

Fold the left edge of the sheet into the center, then fold the right edge over the left edge (do not go past the left edge). You should have a strip of dough about 3 inches wide with the filling tucked into the bottom.

Starting with the lower left corner, fold the corner of the strip over to the right edge to form a triangle. Continue folding up, then over, until you reach the end of the strip.

Place folded triangles onto the prepared baking sheet and brush the tops with any leftover melted butter.

Bake until golden and flaky, about 15 minutes. Cool for 5-10 minutes before serving.