For many recipes it is necessary to separate the egg yolk from the egg white.
There are many different ways to accomplish this. This tip explains the traditional method of breaking an egg and switching the yolk back and forward from one half of the egg to the other.

It can't be done after the yolk is broken/pierced. But, of course, separating white from yolk requires that you break the eggshell to separate them.

You need 2 bowls and a couple of eggs.

Break the egg in halves along its equator by cracking it on the side of a bowl. Break the shell gently in order to keep the yolk in one piece. Once the shell is broken, carefully separate the two halves and hold them side up, like cups, one in each hand. One of them contains egg white and the yolk, and the other only egg white.

Empty the egg white from the half shell without yolk into one of the bowls.
Slide the yolk from the other half shell into the empty shell, taking with it as small an amount of egg white as possible. Pay attention to the yolk, it should not be pierced at the jagged shell edges.

Repeat the process of emptying the half with only the egg white and sliding the yolk to the other half until there is no longer separable egg white remaining. Generally, it is no problem if there is a tiny amount of whites with the yolks, so not separating perfectly is no problem.

Remember: verify that the yolk is whole before emptying the egg white into the bowl. That way you don't spoil all your whites with one broken yolk.