Mix the butter (pre-set at room temperature for 2-3 hours), and while continuing to stir, add the yogurt and flour. Knead dough, which is left to cool for 2 hours, and then rolled out crust, thick 0.5 cm. Cut rind into squares with side 8 cm. In the middle of each square put the filling made from ground walnuts, sugar and cinnamon. Folding pieces of triangles that are pressed at the edges with a fork to stick together. Arrange in a baking dish and bake in a moderate oven. More hot, well cooked pieces are rolled in powdered sugar.