Take a Non-Stick pan, add some butter to the pan. Then you can either grate or slice your potato and put in the pan. Keep the pan on low flame and allow the potato slices to form a bed kind of a thing. After some time turn the potato on the other side ( as a whole bed ).

Next cut your mushroom into slices & put it over the so formed potato bed, cover the pan for some time and let it cook for about 2-3 mins (depending on the pan).

In a other bowl beat your eggs along with chopped onion, chillies, & basil/mint. Add some salt, beat well.

Once the the potato-mushroom bed is formed, pour your egg mixture on the bed easily. Cover it & let it stand for sometime until you can turn the omelette the other side (this usually takes some time, but be patient :p )

Finally turn it the other side allow it cook completely. Take it out from the flame and cut into slices. Serve Hot.