It demands a certain honesty to be able to eat these. We eat eggs without a second thought. We kill the duck and cook it with no hesitation. Why then do we get squeamish when we are faced with a developing embryo in a shell?

As China gets more urbanized, it is harder to find a well-cooked huozhuzi, but it wasn't so very long ago that the only bits of protein our grandparents could afford came from this half-developed egg.

The best time to eat a huozhuzi is when the eggs have been fertilized and sitting for about two weeks to 20 days. At this stage, the little bird would have just formed its bones and some flesh, but the yolk is still its main nutrition.

The eggs are washed well, then steamed or boiled. The top of the egg is carefully cracked, and the first mouthful of juices sipped clean before the rest of the shell removed.

The infant bones are extremely soft and can be crunched up whole. The yolk, large and light yellow after cooking, is also enjoyed dipped in salt or soy sauce.

While the popularity of the huozhuzi wanes at home, its popularity abroad has only grown.

In the Philippines, entire villages take part in the production of balut, from the rearing of ducks to selection and incubation of eggs.

The cooked products are sold to vendors who insulate the eggs in heavy cotton to keep them warm and disperse to markets and night markets where the balut literally fly off the shelves.