If using cashews, soak them for thirty minutes, drain and set aside.
Clean the mushrooms with a paper towel or dry cloth to remove any dirt. Washing the mushrooms will add more moisture to the already natural high water content in the mushrooms. We used commercially cultivated Bella mushrooms. However, if you use wild mushrooms, please clean them with water and dry them with a paper or cloth towel. If the mushrooms are small, less than an inch, leave them whole. Slice the larger mushrooms in half.
Heat the oil in a heavy-bottomed pan on medium heat. Add the onions and sauté them until they start browning on the corners or edges. Add the ginger and garlic pastes and continue to sauté for two more minutes. Add the cumin, red chili, coriander, and turmeric powders and sauté the mixture for one more minute. Add the tomato paste and sauté for about a minute, or until fragrant. Add the chopped tomatoes and continue to sauté until oil starts pooling around the edges of the mixture. Adjust the heat throughout the process and lower it if necessary to prevent the spices from burning.
Add the mushrooms and salt and mix well until the mushrooms are well coated with the spices. Cover the pan and let the mushrooms cook for another 10-15 minutes. Add the garam masala, mix well and turn the heat off. Since mushrooms naturally release water, there is no need to add additional water.
Garnish with the cilantro and serve hot with naan or steamed rice.