In a large bowl, mix together the cottage cheese, eggs and feta cheese until well blended.
Brush melted butter onto one sheet of the filo pastry at a time, and layer the sheets in the bottom of a 23x33cm baking dish until you have 7 sheets. Let the sheets rest up against the sides of the dish as well. Spread the cheese mixture over the filo, then repeat the process with 7 more sheets at the top, tucking in the sides around the edges.
Bake for about 30 minutes in the preheated oven, until golden brown and crisp. Cut into squares and serve warm.