Marinate the cleaned mushrooms with ginger-garlic paste, red chilli powder, turmeric and salt for 20 minutes.
In a medium sized pan, cook the marinated mushrooms over medium heat till soft. If needed, you can add very little water while cooking if the mushroom doesn’t release enough moisture. Let the water in the mushroom evaporate. This takes about 5 minutes.
Heat oil in another large nonstick pan over medium heat. Add onions, sauté for a minute and transfer the above mushroom mixture, add curry leaves and adjust salt if needed and fry.
Roast for 10 to 15 minutes till the mushroom turns golden brown in colour and is coated with all the spices. Now add the garam masala, crushed pepper and green chilies, stir for 2 to 3 minutes and turn off the heat.
Garnish with coriander and serve as a side-dish with steamed rice and curry.