For gravy soak cashews in water for 15 min. Now take chopped tomatoes, soaked cashews, ginger and green chilli in a blender and make puree of it. Heat oil in a pan and add hing and cumin to it. Now add puree and all spices to it and cook for 5 min. Once it's cooked add potatoes to it and cook further 5 min. Stuffed dum aloo is ready. Serve it with any paratha or poori.