Boil the pasta in a boiling pan with a pinch of salt. See the instructions on the packet for perfect timing. Drain and keep aside.
Put a pan on medium heat and add some butter. When the butter starts to bubble up put the mushrooms in it. Saute them, and make sure you see a bit of liquid in the pan. If the mushrooms have soaked up the butter you can add some oil/butter in it.
Now add the white flour (maida), stir until the flour taste fades away (about 1 minute.)
Slowly pour in the milk and stir constantly to avoid lumps.
Let the sauce cook for 3-4 minutes in medium heat, until it is thick. Then add salt, pepper, dried parsley and mustard powder. Stir well.
Lastly, grate the parmesan and cheddar in the sauce and add the boiled pasta.
Give it a good toss, heat off.
Serve hot and enjoy this slurpy dish with an accompaniment of your choice.