Flour, the oil and the butter are mixed in order to obtain crumbs. Yogurt is boiled with soda and add to the flour mixture. Must be worked to a smooth dough. Then it tear balls, flatten with hands to become flat. In the middle put the filling made from crushed feta cheese, potatoes and savory. Then superimposing so as to obtain a sort of shells. Brushed with egg yolk and arrange in a greased baking dish. Bake at 200 ° C until lightly browned.