Preheat oven to 400° F. Heat oil in heavy pot and sauté onion for one minute. Add carrots, celery, mushrooms, shoyu, and tempeh. Sauté another 2 to 3 minutes. Add 1/2 cup of soup stock and sweet potatoes. Cover and simmer on medium-low until sweet potatoes are just tender. Add remaining ingredients except potatoes. Mix, cover, and bring to a boil. Place in a casserole dish. Top with potato slices, sprinkle with salt and pepper, and bake uncovered for 1 hour or until potatoes are tender and slightly browned. Remove and serve.
Per serving - 172 calories, 4 g fat (21% calories from fat), 8 g protein, 27 g carbohydrate, 8 g fiber, 0 mg cholesterol, 573 mg sodium