What is in My hand

Someone asked Nasrudin to guess what he had in his hand.“Give me a clue,” said the Mulla.“I'll give you several,” said the wag. “It is shaped like an egg, egg-sized, looks, tastes and smells like an egg. Inside it is yellow and white. It is liquid within before you cook it, coalesces with heat. It was, moreover, laid by a hen…”“I know!” interrupted the Mulla. “It is some sort of cake.”