A ballut is a fertilized duck embryo that is boiled alive and eaten in the shell. In the Philippines, balut eaters prefer salt and pepper and/or a chili and vinegar  mixture to season their eggs. The eggs are savored for their balance of textures and flavors; the broth surrounding the embryo is sipped from the egg before the shell is peeled, and the yolk  and young chick inside can be eaten. All of the contents of the egg may be consumed, although the white may remain uneaten; depending on the age of the fertilized egg, the white may have an unappetizing cartilaginous toughness. In the Philippines, balut have recently entered haute cuisine by being served as appetizers in restaurants, cooked adobo style, fried in omelettes or even used as filling in baked pastries. In Vietnam, balut are eaten with a pinch of salt, lemon juice, plus ground pepper and Vietnamese coriander leaves (southern Vietnamese style).

Fertilized duck eggs  are kept warm in the sun and stored in baskets to retain warmth. After nine days, the eggs are held to a light to reveal the embryo inside. Approximately eight days later the balut are ready to be cooked, sold, and eaten. Vendors sell cooked balut from buckets of sand (used to retain warmth) accompanied by small packets of salt. Uncooked balut are rarely sold in Southeast Asia. In the United States, Asian  markets occasionally carry uncooked balut eggs. The cooking process is identical to that of hard-boiled chicken eggs, and baluts are eaten while still warm.

Duck eggs that are not properly developed after nine to twelve days are sold as penoy, which look, smell and taste similar to a regular hard-boiled egg. In Filipino cuisine, these are occasionally beaten and fried, similar to scrambled eggs, and served with a vinegar dip.

The age of the egg before it can be cooked is a matter of local preference. In the Philippines, the ideal balut is 17 days old, at which point it is said to be balut sa puti ("wrapped in white"). The chick inside is not old enough to show its beak, feathers or claws, and the bones are undeveloped. The Vietnamese often prefer their balut mature from 19 days up to 21 days, when the chick is old enough to be recognizable as a baby duck and has bones that will be firm but tender when cooked. In Cambodia, it is eaten while it is still warm in its shell. It is served with nothing more than a little garnish, which is usually a mixture of lime juice and ground pepper.