Once hot, add cubed bell pepper and saute for 1-2 minutes or till the sides start to get very light brown. Set aside.
In the same pan, heat 1 teaspoon of oil and add sliced white mushrooms.
Saute till mushrooms turns golden brown in color. This will take few minutes as mushrooms first release a lot of moisture and then start getting brown. Set aside.
In a pan dry roast coriander seeds and whole dry red chili for 2-3 minutes or till you get a nice aroma.
Transfer roasted spices to a spice grinder and grind to a fine powder. Set aside.
In a pan, heat 2 teaspoons of oil on medium heat. Once oil is hot, add chopped red onions.
Cook the onions till they they start turning light golden in color, then add ginger garlic paste and cook for 2-3 minutes or till the raw smell goes away. [Tip: use fresh ginger-garlic paste for better taste and flavor]
Add tomato puree and cook for 5-6 minutes on medium heat.
Then add the roasted spice powder and cook 1-2 minutes. If you the spices can burn, add little water.
Add water, kashmiri red chili powder, sugar, vinegar and salt and let it all come to a boil.
Add cream and mix and finally add in the sauteed bell pepper (capsicum) and mushrooms and mix. Add crushed kasuri methi & mix.
Sprinkle garam masala on top, garnish with chopped cilantro and serve kadai mushroom hot with naan or roti.