Take the flour, baking soda, and salt in a large mixing bowl. Add the oil and yogurt to it. Start kneading by adding enough water to make a fairly stiff dough.
Knead for another 5 minutes or until the dough begins to relax a little without adding any extra water.
Cover with a damp kitchen towel or place in a large airtight container for 1 to 2 hours.
Boil and cool potatoes and then mash the potatoes.
Finely chop the chilies and finely chop the coriander leaves (Hara Dhaniya)
Add the chilies, coriander (Hara Dhaniya) and spices to the potato mix. Squeeze a few drops of lemon on top and sprinkle salt.
Mash everything well, taste and adjust salt and sourness according to your taste. Set aside.
When ready to make Kulcha heat a thick bottomed griddle or tawa over medium heat.
Divide the dough into 6 or 8 equal sized portions and form into smooth balls.
Divide the filling equally into the same number of portions and form each into a ball.
Dust the flat working surface and rolling pin with a little flour and press a dough ball into a thick flat dish about 3 to 4 inches in diameter.
Cup one palm and place the disc on top and gently push down to shape like a small bowl. Place one portion of the filling in the depression and pull the dough over it from all sides and pinch it close.
Return to the rolling board and roll into a circle like chapati but not think like chapati.
If using any toppings press a portion on the top. For dry toppings like nigella seeds it helps to lightly brush the top with water and sprinkle the seeds on top.
Place the Kulcha on the heated tawa (griddle) with the toppings facing up.
When bubbles start forming on top brush the top with a little oil and flip .
Brush a little oil, wait for it to puff up a little more. Flip again to finish cooking both sides evenly.
Remove from heat and put some butter or ghee on top of it and crush it lightly before serving.