Prepare Chappati dough.
Pressure cook Potatoes, peel them and mash them. You can also grate if you want. I use Pav baji masher or at times grate it.
Chop Onions as juliennes, this way you won't have them coming off the paranthas. Chop chillies to small pieces.
Heat a pan with cooking oil, sauté onions and green chillies till the onions are translucent or little brown. We don't want them to be very brown. Add salt while you are frying them.
Remove from fire, and once they are cool, mix well with the mashed or grated potatoes. This is the secret to roll out a non sticky dough stuffed with aloo. You can remove the chillies if you want or leave it. Depends on your chilliness! Mix well and divide to equal portions.
Divide the chappati dough into equal portions, the size of your regular chappatis.
With your palm, flatten a dough and using one hand, press the sides of the ball to form a hallow to fit the potato ball. The middle should be thick and sides should be thin.
After placing the potato ball, close on the sides to completely cover the stuffing. Run it around the palm so that it gets closed well.
Dust some flour and press on the board. Then gently roll out with the rolling pin. The movement should be flip flap, one to ensure you don't press on the parantha and make the stuffed aloo to come out.
Heat a tawa and smear oil. Once the parantha is rolled out, with all the sides evenly spread, gently remove and place on the hot tawa. Reduce the flame to medium and let it bubble up. Turn it around and spread oil around the paranthas. The paranthas taste better if the oil is spread to the sides too.
Drop a dab of butter if you like!
Once both the sides are cooked, remove and serve hot. Its crispy while its hot and very soft when its cool.