Quarter your bean curd squares then cut into 2 triangles. Turn each on longest side and cut thru to make 3 thin triangles from each. Set aside.
Cover mushrooms with 3/4 cup boiling water and soak 1 hour. Lightly squeeze to let liquid drain back into bowl [NOTE this is where you get the mushroom liquid. The soaking water not the rinse step] then rinse briefly and squeeze dry. Destem and cut cap into 1/2 inch wide slices. Place scallions, ginger, mushrooms and curd on work tray. Measure mushroom liquid if you are short 1/2 cup add some stock or water.
Heat large heavy skillet over high until hot. add oil. Swirl. heat for 15 seconds. Lower heat to med and place scallions and ginger in and stir rapidly a few times. Add the sherry, soy, sugar and mushroom liquid. As it sizzles to boil add mushrooms and bean curd. Turn gently a few times. Adjust heat to maintain gentle simmer. Cover and simmer for 10 to 12 minutes. Turn contents half way thru.
You should be minus the liquid or close to it at this point. Add the oil and turn once more. The serve.