TIP: After separating eggs for a recipe, pour the remaining egg into an airtight container and freeze. To prevent the eggs from gelling add a pinch of salt for cooking or a heaping teaspoon of sugar for baking for every 4 yolks. Transfer the frozen egg to the refrigerator the day before using and let the egg parts thaw overnight.
When I discovered this trick, I was so thrilled. My "world" famous cake calls for four egg whites and I was always stumped on how to save the yolks. I hated throwing them out. Hope this tip is useful for you. Enjoy!! :-)