What you see: Egg cracked during boiling, resulting in an oddly shaped egg white, and strings and clumps of egg white in the cooking water
What it is: Just what you’d expect loose egg white to do in boiling water!
Eat or toss? Eat! This isn’t so different from poaching an egg. It just happened when you thought you were hard-boiling in the shell.
Perhaps they're just creative, rebellious types. You know, the eggs that manage to slam into each other while boiling (or, um, while I'm putting them into the pot a little too quickly). Then, they crack, release some of their white into the water, and let it solidify around them in an assortment of shapes that look, well, sculptural. These free spirits can, however, be a bit disturbing on a plate.
But, not to worry! Whether the egg turns out bulbous and distorted, like the one gracing my salad pictured below, or creates cloudlike wisps of white, like the egg pictured in the pot above, it's still perfectly safe to eat. Since it's been thoroughly heated, anything potentially harmful has been killed. One caveat though— since the shell has cracked, pathogens might target that opening in the shell. Just make it a priority for peeling and eating.
To avoid these free-form hardboileds, try this alternate method: put the eggs in a pot and cover with water, then bring to a boil. Once the water is boiling, cover the pot, remove from heat and let sit for 10 - 15 minutes (depending on the size of the eggs). Once they've cooked, either eat them warm right away, or cool them in an ice bath to keep them fresher longer. In addition to preventing those funky cracks, this method is said to keep the eggs from getting rubbery and to prevent that icky green ring that sometimes appears on the yolk.
Pat Curtis - Head of Prestage Department of Poultry Science - North Carolina State University
How to Hard Boil An Egg - The Kitchn
Hard Boil Eggs - IncredibleEgg.org
What Happens When An Egg Cracks While Hard Boiling?
Is it breakfast? Or an abstract sculpture?