Step 1

Add the bananas to a mixing bowl and mash well. Add the yogurt, baking soda, baking powder and salt and mix well. Add the flour and mix it slowly with a wooden spatula until everything comes together. Flour your clean hands lightly, turn it out onto a floured surface and knead the dough slowly. If the dough is wet, add more flour, 1 tablespoon at a time, and roll it back and forth to get it smooth. Place the dough in a bowl, cover and let rest for 2 hours.

Step 2

Pour the vegetable oil into a pot to a depth of 3 to 4 inches (7.5 to 10 cm), place over medium-high heat and bring to 350°F (180°C) on a deep-frying thermometer.

Step 3

Divide the dough into 14 to 16 equal portions. Add some nigella seeds to each piece and roll them to about 4 inches (10 cm) in diameter and ½ inch (1.3 cm) thick. Carefully add the rolls to the hot oil in batches and fry them over medium to medium-low heat for about a minute on each side, or until golden brown. Remove from the oil with a spider and drain on paper towels. Bring the oil back up to temperature in between batches.