Elixir Soup is a creation of Link's Grandma, and it is extremely nutritious. Not only does it completely refill your health and magic, but it also doubles your attack power until you are hit. It can only be acquired after healing her with a Fairy, and later visiting her with an empty bottle. There are 2 servings per bottle, but you may only carry one bottle of it at a time, as she will not offer you any if you already have some. Once you drink it all, she will gladly make more for you.
 How to Have Extra Servings
If you have at least 2 empty bottles, have grandma fill one up with soup, and then set it to Y. Press Y, and then immediately after, press start and switch the full bottle with an empty bottle. The full bottle will stay full and the empty bottle will end up with 1/2 a serving.