Each one of us cooked the hard boiled eggs. You think, what the secret might be there? But you are not right. Did you ever paid attention to the greenish stripes along the edge of the yolk? This suggests that the eggs were cooked wrong. Properly cooked eggs has a white protein and uniform yellow yolk.
It's very simple to do.
1. Put raw eggs in a bowl and fill it with water, so the water covered them for at least 1 cm
2. Put it on slack fire to slowly boil the water.
3. The moment, when the water start to boil, cover the bowl a tight lid and remove it from the heat.
4. Do not open the lid exactly 13 minutes. (this is very important - 13 minutes !)
5. All, your eggs are perfectly cooked hard-boiled.
Bon Appetit! :-))