How to Make It
In a medium bowl, combine the feta, cottage cheese and Parmesan. Stir in the flour, eggs and pepper.
Line 2 baking sheets with parchment paper. Lay 1 sheet of phyllo on a work surface with the long side facing you. (Keep the remaining phyllo covered with plastic wrap and a damp towel.) Brush the wrap lightly with some of the butter; top with a second sheet and brush with more butter. Cut the pastry lengthwise into four 12-inch-long strips, Mound a scant tablespoon of the cheese filling in the center of the end of each strip. Working with one strip at a time, fold the bottom edge up to meet the left edge and form a triangle. Fold the triangle up, then over to meet the right edge, keeping its triangular shape. Continue folding up the length of the phyllo, folding the triangle lightly. Brush the top with butter and set it on one of the baking sheets. Continue making triangles with the remaining phyllo and filling.
Preheat the oven to 400° and position 2 racks in the upper and lower thirds of the oven. Bake the triangles for about 16 minutes, or until golden and crisp, switching the pans halfway through cooking. Let cool briefly, then serve warm.