Balut

Balut is a fertilized developing egg embryo that is boiled or steamed and eaten from the shell. It is commonly sold as street food, commonly eaten with salt and vinegar, most notably in the Philippines, Cambodia (Khmer: ពងទាកូន, paung tea kaun), and Vietnam (Vietnamese: trứng vịt lộn, hột vịt lộn), and also occasionally in Thailand (Thai: ไข่ข้าว, romanized: khai khao). The length of incubation before the egg is cooked is a matter of local preference, but generally ranges from two to three weeks.

Source: Wikipedia