so next time you're trying a new recipe (Usually a pie recipe) and you don't want to throw away egg whites, you can replace 3 egg yolks for 1 whole egg.
Does it makes a difference in a recipe? a little bit. Like in pastry cream, you have to use egg yolks, but if you use an entire egg instead, it might be a bit gooey, but still good, people usually don't notice the difference.
Try it !