First prepare the filling. Peel and cook the potatoes till they're very soft. Mash them very well so there are no lumps left and it is smooth.
Heat the oil in a pan and add the ginger, garlic pastes and chopped onion. Saute everything till the onions soft and translucent. Add the spice powders and saute, over medium heat, for a minute. Then add the green chillies, potatoes, salt and chopped coriander.
Mix everything well and then take off the heat. Allow to cool and divide the mixture into 12 equal portions. Roll the portions into balls.
Then make the dough. Put the whole wheat flour, salt and oil in a deep bowl and whisk together. Add the water about 1/4 cup at a time and knead until your dough is soft (but not sticky) and elastic. Divide the dough into 12 equal portions and roll each into a ball.
Now make the parathas. Take ball of dough and roll it out into a 3" circle lightly dusting with whole wheat flour if necessary.
Place a ball of mashed potato in the centre of the dough circle. Bring up the sides of the dough circle around the potato ball and enclose it completely, pinching dough on top to close and seal the filling.
Flatten it slightly, dust lightly with whole wheat flour, and roll out into a 1/4 u201cthick circle. Make sure that the filling doesnu2019t come out while rolling. Use the rolling pin lightly when rolling the paratha out.
Cook the paratha on a hot tawa/ skillet over medium heat till light brown spots appear on side. Cook similarly on the other side. Brush lightly with oil and again cook the paratha on both sides till the brown spots deepen a bit one.
Repeat with remaining dough balls and potato filling.
Serve hot with fresh thick plain or seasoned yogurt (home made, if possible), thin slices of raw onion and pickles.