Heat the oil in a large pan, like the All-Clad. Add the onions, saute a couple of minutes until it starts to soften, then add the tomatoes, paprika, and turmeric. Cover with a lid and cook until the tomatoes are completely broken down. Stir occasionally during cooking.
Add the green peppers and mushrooms, stir, and continue to cook, covered for another five minutes.
Add the tofu and the karahi masala, a tablespoon at a time. Add enough masala to your taste, and store the remaining in an airtight jar for another use.
Add 1/2 cup of water, cover the pan, and cook for another 10 minutes, stirring occasionally.
Add the cashew paste and salt to taste.
Sprinkle the coriander and mint leaves, stir, and turn off the heat.