Heat the pan at medium low heat and dry roast cumin seeds, fennel seeds, coriander seeds, black pepper corns and dry red chiily till you get nice roasted aroma. Stir them continuously to avoid burning.
Once spices are nicely roasted transfer them in a bowl and let them cool down. When spices are cold enough grind them to a course powder.
In the same pan heat 1 tsp of oil at medium heat, add chopped onions, saute and cook till onion turns brown. It may take 7-8 minutes.
Once onion is brown enough, add chopped tomatoes and salt. Saute and cook till tomatoes become mushy. Now transfer them in a bowl and let them cool down.
When onion and tomato masala is cold enough grind it to a paste using 2-3 tbsp of water.
Now heat the pan at medium heat and add 1 tsp of oil and butter. As the butter melts add ginger garlic paste and stir continuously till raw smell of garlic disappears.
Now add dry karahi masala which we made earlier and stir for few seconds. Add onion tomato paste and cook for few more minutes till masala looses oil.
Now add dry karahi masala which we made earlier and stir for few seconds. Add onion tomato paste and cook for few more minutes till masala looses oil.
Now add washed mushrooms and cook in the gravy for 3-4 minutes. Once mushrooms are slightly roasted add bell peppers and onions. Saute for a minute and add 1 cup of water. Boil the gravy for 3-4 minutes.
Switch off the heat. Karahi mushroom is ready to serve. If you like garnish it with cream.