Make the dough:
Mix the flour, salt and oil. Add enough water and knead to make a stiff but pliable dough. Set aside for at least 30 minutes.
Make the filling:
Heat the oil. Add the grated onions, ginger and garlic. Add some salt and stir-fry the onions until they start to turn a light golden-brown.
Add the cayenne, cumin, turmeric and aamchur and saute for a minute.
Add the mushrooms and cook, stirring frequently, until the mixture is quite dry. Add the besan and salt to taste and stir-fry another two minutes or until there is no visible moisture. The mushroom mixture will hold together when you ball it up.
To put together the parathas. divide the dough into four pieces.
Roll each into a smooth ball.
Take one ball and flatten it with your fingers. Prep the surface you will roll the bread on by flouring it, and flour the rolling pin as well.
Roll the dough into a disc about four inches in diameter.
Take one-fourth of the mushroom mixture and make a ball. Place it in the center of the disc of dough.
Gather the corners of the dough on top, like a dumpling. Seal at the top, roll into a ball, and flour the top and bottom.
Roll into a disc about six to seven inches in diameter.
Heat a cast-iron or nonstick griddle. Roast the paratha until golden-brown spots appear on the underside, flip over and cook the other side. Spray a little oil for an extra-crispy paratha.