If you’re not sure if an egg is properly hard-boiled, simply spin it. If it’s not fully cooked, it will wobble.
When hard-cooking eggs in the shell, never place them in boiling water. This will almost always cause them to crack due to the sudden change in temperature.
Slow-cook eggs to help prevent the egg white from becoming tough and rubbery. Simply place the eggs in a large pot and cover eggs with cold water. Bring the water to a boil and remove from heat. Cover pot and let sit for 17-20 minutes.