Beat the softened butter, yogurt and yolks together until creamy. Mix the baking powder and flour together and gradually beat into the creamed mixture. Knead well until smooth and the dough no longer sticks to the fingers. Leave in a covered bowl in a warm room for 2-3 hours to rise.
To prepare filling, mix together the sugar, almonds and cardamom.
Roll out the dough on a well-floured board, fairly thinly, and cut out in 3" rounds. Put 2 tsp of the filling on each round. Damp the edges and seal together, curving them rather like tiny croissants.
Deep fry in hot oil (375 degrees) for about 4 minutes until golden brown. Drain on a paper towel, them while still warm, dredge in cardamom-flavored sugar. When cold, dredge again in the sugar.