Chop the cashew nuts with 1/2 c water in food processor until smooth.
Warm the oil in a large frying pan over medium heat. Saute the cinnamon and cardamom until fragrant. Add the onion, ginger, and garlic. Saute for 3 minutes. Add the tomatoes, cilantro (coriander), chile, turmeric, and garam masala and simmer over low heat until the oil begins to seperate. (about 10 minutes)
Add the salt and water. Bring to a boil. Stir in the mushrooms, peas, and cashew nut mixture. Simmer, stirring occasionally, until the vegetables are tender, about 10 minutes. Serve hot.