Clean spinach leaves well, remove stems and chop leaves and stems separately. In wok or skillet, saute stems, onion and garlic until onions are translucent. Stir in cooked rice. Lay spinach leaves on top of rice mixture. Cover pan and cook until spinach is wilted. Stir leaves into the rice mixture. Add the cheese and season to taste with soy sauce. Stir until the cheese melts and holds mixture together.