To make the first dough, sift the refined flour with the baking powder, soda bicarbonate and salt. Add the yogurt, egg, milk, sugar and a little water.
Knead well to make a medium soft dough. Add a little oil and knead again. Cover with a damp cloth and rest the dough for one hour. Knead the dough once again and divide it into eight equal portions. For the second dough, sift the refined flour with salt. Rub in the butter with your fingertips till the mixture resembles coarse crumbs. Gradually mix in the milk and knead to make a soft, smooth dough.
Cover with a damp cloth and rest the dough for ten minutes. Knead the dough once again, divide it into eight equal portions and shape into smooth balls.
Cover with the damp cloth and rest it for another ten minutes. For the stuffing, mix together the potatoes, onion, salt, green chillies, chilli powder, cumin powder, dried pomegranate seeds and the fresh coriander.
Divide the potato mixture into eight equal portions. Flatten a portion of the first dough, place a portion of the potato mixture in the centre, and fold the dough over to form a ball. Flatten a portion of the second dough and place the stuffed ball in the centre, and roll into a ball. Place on a lightly floured surface and roll gently into a circle.
Heat a pressure cooker. Dip the fingers in a little water and moisten one side of the kulcha, gently press the moistened side of the kulcha onto the inner wall of the pressure cooker, making sure the kulcha is moist enough to stick to the cooker.
Place the cooker upside down over an open flame to make a kind of tandoor. Cook on high heat for two to three minutes, lower the heat and cook for two to three minutes more.
Turn the cooker upright and gently peel the kulcha away from the cooker wall. Brush the hot kulcha with butter and serve immediately. Similarly make more kulchas. You can also cook the kulchas in a preheated oven at 220C/425F/Gas Mark 7 for about eight minutes.