Place tofu in a colander and let drain for 15 minutes.
Meanwhile, prepare cooking sauce and set aside.
Cut tofu in domino shaped pieces, and place between paper towels; gently press out excess water.
Sprinkle with the 1/2 teaspoon salt and set aside.
If you use broccoli, cut off flowerets (if large, cut in half) and slash stems.
Peel thick stalks and thinly slice.
If you use green beans, remove ends and strings; cut in 2 inch long slanting slices.
If you use carrots, cut in 1/4 inch thick slanting slices.
In a 3 quart pan over medium heat, place water, the 1 teaspoon each salt and sugar, ginger, and the 1 tablespoon each oil and sherry.
Bring to a simmer.
Heat 2 tablespoons of the salad oil in a wide frying pan over high heat.
Add mushrooms and cook, stirring, until golden.
Add sherry and the 1/2 teaspoon sugar and cook until liquid evaporates; remove mushrooms and set aside.
Reduce heat to medium and add the remaining 2 tablespoons oil.
Add tofu and cook until flecked with brown (about 3 minutes on each side).
Return mushrooms to pan.
Stir cooking sauce, pour into pan, and cook, stirring gently, until sauce bubbles and thickens.
Keep hot.
Bring seasoned water to a boil.
Drop in vegetables.
Cook until crisp tender (about 4 minutes); drain, then discard ginger.