Preheat oven to 400° F. Heat oil in a heavy pot and sauté the onion for one minute. Add the carrots, celery, mushrooms, shoyu and tempeh. Sauté another 2 to 3 minutes. Add 1/2 cup or soup stock and sweet potatoes. Cover and simmer on medium-low until the sweet potatoes are just tender. Add all remaining ingredients except the potatoes. Mix, cover and bring to a boil. Place in a casserole dish. Top with the potato slices, sprinkle with salt and pepper, and bake uncovered for 1 hour or until the 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