Cut tofu crosswise into pieces the shape of French-fried potatoes.
Heat a wok, coat with oil & sprinkle on the salt.
Add onion, then the mushrooms, stir frying each over high heat for about 30 seconds.
Reduce heat to medium-low and add carrot, green pepper & tofu in that order, sauteeing each for about 1 minute.
Reduce heat to low & add sake, soy sauce, ginger, sugar & water.
Simmer for 3 to 4 minutes.
Stir in dissolved cornstarch & simmer for another 30 seconds.