In a small pan, combine soy sauce, sugar, sake, mushroom water and sesame oil. Simmer the sauce over a slow flame for 5 mins and let cool. Brush soy mixture over sheets, generously. Repeat until all the sheets are in one pile, save left over sauce. Fold three times across the shorter side and cut crosswise in half.
Wrap strips securely with gauze.
Place wrapped items in a steamer for 15'. Take out and remove gauze. Saute strips in a skillet over a moderate flame and fry both sides until golden brown. When risen, spread onto baking sheet and add toppings. Bake in a hot oven.