8 ounces of good feta cheese, crumbled into small pieces
1 cup of grated graviera (or a gruyere-type cheese), grated
2 eggs, lightly beaten
1 tsp black pepper
3 Tbsp finely chopped flat-leaf parsley
12 +/- (17 x 12 inch) phyllo sheets (thawed if frozen). This is about half of one box.
1 stick (1/2 cup) unsalted butter, melted
Combine cheeses, egg, pepper and parsley in bowl with fork. The mixture will be lumpy.
Pre-heat oven to 350°F.
Place two sheets of phyllo on top of one another, keeping remaining sheets covered with wax paper and dampened dish towel, and cut in half lengthwise. Pile the sheets again on top of one another, and again cut in half lengthwise. This will give you 8 individual strips about 3 inches wide by 17 inches long.
Place one strip in front of you, again covering remaining phyllo with wax paper and dampened dish towel. Lightly brush pastry with melted butter. Put 1 heaping teaspoon of filling in lower corner of pastry, and fold corner of phyllo over to enclose filling and form a triangle. Continue folding (like a flag), maintaining triangle shape. Put triangle, seam side down, on large baking sheet and brush top with butter. Make more triangles in the same manner, using all the filling. (Here's a good illustration of the folding technique.)
Bake triangles in middle of oven until golden brown, 20–25 minutes, and then transfer to rack to cool slightly. Serve warm.