To prepare filling, finely chop the stems of mushrooms. Heat a pan. Add butter to it. Do not add all the butter. save a small quantity for basting. Keep the heat low. When the butter melts, add onion, garlic and green chili. Cook till onion softens a bit. Do not brown the onion. Then add chopped mushroom stems. Also add dried herbs and crushed black pepper. Add salt to taste. Cook till all the water evaporates. Add half of the grated cheese, and half of the chopped coriander leaves. Switch off the gas. Mix well.