Combine the potatoes, salt and 2 1/2 tsp green chilies mix gently with the help of forks. Keep aside.
Heat the butter in a broad non stick pan, add the onions and sauté on a medium flame for 2 to 3 minutes or till they turn translucent.
Sprinkle remaining green chilies and cook on a medium flame for 1/2 minute.
Sprinkle the cheese evenly on all the onions and spread the prepared potatoes mixture evenly over it.
Cover the lid and cook on a medium flame for 5 minutes.
Loosen the sides of the rosti with the help of a knife, place a plate inverted on the non stick pan and turn the pan upside down to invert the rosti on the plate.
Serve immediately.
Notes
Par boiled potatoes for this receipe should be 90% cooked.Best accompanied with sour cream.