Prepare the Dough:

1. In a large mixing bowl, combine flours and salt. Add the water, 1/2 cup at a time, stopping as soon as the dough comes together - it should be soft and pliable, but not sticky at all. (You might need to add a little more water or flour to achieve the right consistency.)
2. On a clean work surface dusted with flour, knead the dough for about 5 minutes or until then shape into a ball. Cover with a damp cloth and set aside to rest while you make the filling.

Prepare the Filling:

1. In a large pot of boiling salted water, cook the potatoes until fork-tender, about 15 minutes. Drain and let cool for 5 minutes.
2. In a large mixing bowl, mash the potatoes, then add the onion, chili, cilantro, turmeric, cumin and amchur, if using. Taste and adjust the seasoning with a little salt, if needed.
3. Shape the potato mixture into balls about the size of a ping pong ball.
4. Assembly:
5. Divide the dough into 12 equally-sized pieces, and roll each one into a ball.
6. On a lightly floured work surface, roll out a dough ball into 4" disc. Place the disc on the palm of your hand, and brush lightly with a few drops of coconut oil. Place a ball of filling in the centre, then bring the sides of the dough together to cover the filling and pinch together to seal tightly. Roll gently between the palms of your hands to shape into a ball again, and set aside. Repeat with the remaining dough and filling.
7. Roll out the balls into thick discs, about 6" wide each, being careful not to break the dough to expose the filling inside.
8. Heat a heavy-bottomed skillet over medium-high heat. Place one of the parathas in the skillet and cook, shaking the pan occasionally to make sure it isn't sticking, until the bottom is covered with light golden-brown spots. Turn over and cook the other side until it's also speckled with light golden-brown spots.
9. Brush the top of the paratha with a little coconut oil, then flip over and repeat on the other side. Turn over one last time and cook for about 30 seconds.
10. Repeat this process with the remaining parathas, keeping them warm in the oven between batches. Serve immediately.