IT was an egg-straordinary moment when a mom-of-two cracked open a giant egg and found another fully formed one inside.

    Emma Postlethwaite, 33, was stunned when she found the enormous 167-gram egg that was laid by her hen Wendy at her home in Stoke-on-Trent, Staffordshire, Britain.

    The secondary school teacher filmed the moment she cracked the egg open only to find another standard-size egg inside.

    In the incredible 45-second video, Emma can be heard saying, “Oh, it’s another egg. It’s like a Russian doll.”

    She then cracks open the smaller egg, which also has a yolk and white inside, as her 2-year-old son Austin points at the pan and says, “Egg.”

    The mother-of-two also pops both eggs in the frying pan as her husband Damien, 34, who filmed the video, says, “An egg inside an egg. There you go.”

    Postlethwaite uploaded the video to her Facebook page Thursday evening where it has now been viewed 5,700 times.

    The extremely rare occurrence is known as a counter-peristalsis contraction and is caused when the hen is in the process of forming an egg in her oviduct and another oocyte — the ovum or egg cell that becomes the yolk of the egg — is released too soon.

    Usually hens release an egg cell every 18 to 26 hours but sometimes a second one is released by the ovary before the first egg has completed its journey.

    It is thought that a shock or stress then causes a contraction which forces the first egg to reverse its course meaning the two come together and the shell from the second egg creates a giant egg around the first one.(SD-Agencies)