Boil the potatoes in salted water. Pass them through a masher, stir in the tuna and season with pepper.
Mix together the flour with the melted butter and brandy, and keep adding the salted water bit by bit. Knead well and set aside in a cool place for at least an hour.
Roll out half the pastry on a surface dusted with flour. Place small portions of the filling, cover with the rest of the rolled-out pastry and cut with a pastry cutter.
Fry in olive oil and dust with cinnamon and sugar.