Popular appetizers in many of New England’s Greek communities where they are called Tiropitakia. Work quickly as you make them so the dough doesn’t dry out.
Preheat oven to 425 degrees F. Saute onion and chives in butter and oil, being careful not to let them brown. Add feta and cottage cheese and blend with a fork to combine. Add eggs, one at a time, and beat until mixture is well blended; it will not be perfectly smooth. Melt butter. Take a sheet of dough, butter it, and cut into 2-inch wide strips. Lay one strip in front of you vertically, place 1 teaspoon cheese filling on lower left corner of pastry strip, and fold right corner over to make a triangle. Continue folding from side to side to end of strip. Lightly butter top of finished triangle. Bake 10 to 15 minutes until tops are lightly browned. Triangles can be assembled and frozen, then put into oven and baked without thawing first.