Combine the flour and water in a bowl and knead until it forms a smooth round ball similar to a stiff pizza dough. Cover the dough and set aside. Put the mashed potatoes, red onion, fenugreek leaves, garam masala, and cilantro into a bowl and mix well. Taste for seasoning and add salt, and pepper, to taste. Take a piece of dough about the size of a golf ball and roll it into a disc with your fingers. Lightly dust a work surface with flour and using a lightly-floured rolling pin, roll out the disc into a thin patty (like a tortilla). Place 1/4 cup of the filling into the middle of the patty and then fold the edge of the dough over the mixture and form into a ball, with the filling in the center. Roll out the paratha gently, being careful not to squeeze the filling out. Put a nonstick skillet over medium-high heat and place a paratha into it. Cook until brown bubbly spots appear and then flip the paratha and cook the second side until it is done, about 3 minutes per side. Continue until all the parathas are done.