Combine the remaining sugar, flour, and salt in a bowl. Pour in the yeast mixture, yogurt, water, nigella seeds, and 4 tbsp oil, then mix until a dough forms. Allow the dough to rise in an oiled bowl, covered, for about an hour or until it doubles in size.
Divide the dough into small balls. Roll out each ball into a circle about 1/2 cm thick. Place 1/8 of the kale mixture in the center of each circle and spread it out slightly. Bring the edges of the dough together and seal them. Flip the naan over and roll it out evenly.
Heat a large frying pan over high heat. Place a naan in the pan and cook until the top starts to puff and the underside browns. Flip it over and brown the other side. Brush with butter or ghee and sprinkle with nigella seeds.
