i just learned that to have a perfectly hard boiled egg...there's a rule of 5-five-5...1st: boil water with salt and vinegar 2nd: Put the eggs when the water is completely boiling and let it cook for exactly 5 minutes. 3rd: off the stove and let it rest there for exactly FIVE minutes. 4th: transfer the eggs to a bowl of very cold water and leave it there for another 5 minutes and then 5th: finally you can peel it and tada!!! its perfect!!!