Cut the bean curd into 1x 1-1/2-inch flat pieces. Deep-fry them in hot oil for 2 to 2-1/2 minutes, until the surfaces are somewhat firm and yellow. Drain thoroughly. Soak the mushrooms in boiling water for half an hour. Drain. Discard the stems and cut the caps into halves. Cut the onion into thin slices. Break the broccoli into individual florets and cut the stem into 1-inch wedges. Heat the vegetable oil in a large frying pan or wok. When hot, add the onion, ginger, broccoli stems, and mushrooms and stir-fry in the hot oil for 2 mintues, to season the oil. Add the broccoli and stock and continue to stir-fry for 1-1/2 minutes, and then cook, covered, for 1-1/2 minutes. Uncover the pan or wok, pour the sauce ingredients over the contents, and continue to turn and stir-fry all ingredients together for a further 1-1/2 minutes. Serve with rice and other dishes.