Drain tofu. Mix mushrooms and preserved vegetable in medium bowl. Mix 5 tablespoons water and next 8 ingredients in small bowl. Heat vegetable oil in wok or heavy large skillet over high heat 1 minute. Add green onions, garlic and ginger and stir-fry 1 minute. Add mushroom mixture and stir-fry 1 minute. Stir broth mixture. Add to wok with peas and stir-fry until sauce boils, about 1 minute. Add tofu and toss gently to coat with sauce. Cook 2 1/2 minutes, tossing gently. Divide between plates. Sprinkle Szechwan powder over (recipe follows). SZECHWAN PEPPERCORN POWDER: (Makes about 4 teaspoons) Heat heavy frying pan or wok over medium-low heat 1 minute. Add 1 tablespoon whole Szechwan peppercorns and stir until aromatic, about 4 minutes. Transfer to blender. Cool 10 minutes. Blend to a fine powder. Store at room temperature.