Cook pasta in 2 quarts boiling water for 5 minutes, drain and rinse under cold water, and drain again.
While the pasta is cooking, prepare the tofu ricotta. Place the tofu, water, ume plum vinegar, scallions and shoyu in a blender. Blend until creamy. Place the tofu ricotta in a medium mixing bowl, add the spinach, and mix well. Stuff each manicotti shell with spoonfuls of tofu cream. Place in an oiled baking dish. Preheat the oven to 350°.
To prepare the sauce, heat oil in a medium skillet or saucepan and sauté the garlic for 1 minute. Add the onions and mushrooms, sauté 2 minutes. Pour in the sauce and shoyu. Cover and simmer for 10 minutes.
Pour the sauce over the stuffed manicotti, cover baking dish and bake for 30 minutes.
Per serving - 151 calories, 7 gram fat (40% calories from fat), 11 gram protein, 13 gram carbohydrate, 2 gram fiber, 0 milligram cholesterol, 319 milligram sodium