Thai basil has small purple leaves and a stronger taste than sweet basil; if unavaliable, use the latter. The longer you marinate the tempeh, the more flavorful it will be. We liked this dish best with soy tempeh, but any variety (five-grain, three-grain, soy-rice) will work.
To prepare tempeh, combine first 4 ingredients, stirring with whisk. Add tempeh, turning to coat. Let stand at room temperature 20 minutes to 4 hours, turning once. Remove tempeh from marinade; discard marinade.
Heat 1 1/2 tablespoons olive oil in a wok or large nonstick skillet over medium-high heat. Add tempeh; sauté 2 minutes. Remove tempeh from pan.
To prepare spinach, heat 1 1/2 teaspoons olive oil in pan over medium-high heat. Add 1 1/2 tablespoons sake, salt, and spinach; stir-fry 1 minute or until spinach wilts. Remove spinach from pan with a slotted spoon.
Combine sugar, 3 tablespoons soy sauce, water, and juice; set aside. Heat 1 tablespoon olive oil in pan over medium-high heat. Add onion and garlic; stir-fry 3 minutes or until onions are tender. Add tempeh, sugar mixture, and basil, stirring to combine. Cook 2 minutes or until heated, stirring frequently. Spoon tempeh mixture in the center of a serving platter; arrange spinach around tempeh. Serve with rice.