Directions

1. 1. Combine the flours, salt, and ajwain in a food processor. Turn the machine on and add the 2 tablespoons of oil and 3/4 cup water through the feed tube. Process for about 30 seconds, adding more water, a little at a time, until the mixture forms a ball and is slightly sticky to the touch. If dry, add another tablespoon or two of water and process for another 10 seconds. (In the unlikely event that the mixture is too sticky, add flour, a tablespoon at a time.) Remove the dough and, using flour as necessary, shape into a ball; wrap in plastic and let rest while you make the potato mixture. (Or refrigerate for up to a day or freeze for up to a week.)
2. 2. Put the potatoes in a large saucepan and add water to cover and a large pinch of salt. Turn the heat to high, bring to a boil, and adjust the heat so the mixture simmers steadily; cook until the potatoes are tender, 15 to 20 minutes, then drain. Mash with the chile, coriander, a large pinch of salt, some pepper, and the lemon juice; taste and adjust the seasoning (you may prefer more chile; sometimes aloo paratha are quite hot).
3. 3. Set out a bowl of flour and a small bowl of neutral oil, with a spoon or brush, on your work surface. Lightly flour your work surface and your rolling pin. Break off a piece of dough about the size of a golf ball. Toss it in the bowl of flour and then roll it in your hands to make a ball. Flatten it into a 2-inch disk, then use a floured rolling pin to roll it into a thin round, about 5 inches in diameter, dusting with flour as necessary.
4. 4. Mound about 2 tablespoons of the filling into the center of one of the rounds of dough. Bring the edges of the round up over the top of the filling and press them together to make a pouch. Press down on the "neck" of the pouch with the palm of one hand to make a slightly rounded disk. Turn the disk in the bowl of flour and roll it out again into a round 6 to 7 inches in diameter. Pat it between your hands to brush off the excess flour. Put the paratha on a plate and cover with a sheet of plastic wrap. Continue to roll all of the remaining dough into paratha and stack them on the plate with a sheet of plastic wrap between them. You can keep the paratha stacked like this for an hour or two in the refrigerator before cooking them if necessary.
5. 5. Heat a nonstick skillet or griddle over medium-high heat for a minute or two, then put a paratha (or two, if they'll fit) on it and cook until it darkens slightly, usually less than a minute. Flip the paratha with a spatula and cook for another 30 seconds on the second side. Use the back of a spoon or a brush to coat the top of the paratha with oil. Flip and coat the other side with oil. Continue cooking the paratha until the bottom of the bread has browned, flip, and repeat. Do this a few times until both sides of the paratha are golden brown and very crisp, 2 to 3 minutes total for each paratha. As the paratha finish, remove them from the pan and brush with melted butter if you wish if you're going to serve hot; otherwise wait until you've reheated them. (You can reheat them in a 300°F oven or by recooking them in a dry pan.)