How do you reliably kill the ice golem things in the Ice Cave?

There are enemies made of ice, who also breathe ice, in the Ice Cave. I found that you can draw yourself to them with the hookshot, but sometimes they would instantly freeze me if I did that. They were immune to the bow.

How can you reliably approach and attack without getting frozen or otherwise damaged?

This is a Freezard. Watch the timing of their frost breath. It is predictable. Wait for them to finish a breath, then hookshot to them and pound them with your sword.

Din's Fire is also effective against them. Also, if you find yourself back in the cavern for any reason later, you can also dispatch them with Fire Arrows after you obtain them.