To make the peanut sauce, mix all the ingredient in a bowl till well combined. Taste and correct the balance of flavours in the sauce. Thin with a tablespoon or two of water if needed.
Toss the tofu cubes in cornflour and salt so that all the pieces are coated. Heat 1 tbsp oil in a frying pan on medium flame and add the tofu making sure the pieces are spread out in a single layer and not touching. Fry the pieces till lightly golden on all sides. Remove and set aside.
Fry the cashews in the same pan for a minute till they're golden. Set aside.
Add the remaining 1 tbsp oil to the pan and fry the ginger an garlic for a few seconds. Then add the mushrooms, carrots, capsicum and peas and fry on medium heat. Stir fry the vegetables so that they are lightly browned, and still crunchy.
Now put in the tofu and fry for 5 seconds. Reduce the flame and pour in the sauce, and mix well. Simmer for 3-4 minutes, adding a little water if required to prevent the sauce from thickening too much. Add the fried cashews, mix and serve hot.