1. Place mushrooms in a large bowl. Bring stock to a boil, and pour over mushrooms. Let stand 30 minutes or until softened. Strain mushrooms, reserving stock, and squeeze excess liquid into bowl. Slice mushrooms thinly; discard any tough stems.
2. Heat vegetable oil in large saucepan over medium heat. Add garlic and next 3 ingredients. Stir in mushrooms. Cook about 2 minutes. Add reserved stock, soy sauce, vinegar, and sesame oil; simmer about 3 minutes. Add tofu and turkey, and simmer about 3 minutes or until heated through. Stir in cornstarch mixture to thicken, if desired, and simmer about 2 minutes. Gently stir in egg to form thin ribbons. Remove lemongrass pieces, season with salt and pepper, and serve. Garnish, if desired.