Preheat the oven to 400 degrees Fahrenheit (200 degrees Celsius). Line a baking tray with baking paper.
Brush pastry: If using yufka pastry, place one pastry sheet on the working surface. Using a kitchen brush (silicon), lightly brush the pastry with the brushing mixture. Next, place the second sheet of pastry on top and brush again. Finally, place the third sheet of pastry on top.
Fill: Place ½ of the filling at the narrow bottom side of the pastry, leaving some free place at the bottom and on the margins.
Fold the margins of the pastry over the filling. Then fold the lower part of the pastry over the folded margins and the filling. Roll the pastry to form a thick “sausage.” Place it on the baking tray.
Repeat with the other three yufka pastry sheets to make a second roll.
If using filo pastry, place two pastry sheets on top of each other on the working surface. Brush with some of the brushing mixture using a silicone kitchen brush. Place the following two filo pastry sheets on top and brush again. Next, place a single filo sheet on top of that. Add the filling, roll the “sausage” as described above, and make a second roll using the remaining pastry sheets.
Brush both rolls with some remaining brushing mixture and sprinkle the rolls with nigella seeds.
Bake for about 30 minutes or until deeply golden and crisp.