Ajitama ramen eggs are cooked in boiling water for 7 minutes to cook the whites until hard, then transferred to ice cold water to stop the cooking process and keep the yolks nice and jammy. They're then marinated in a soy sauce mix. Onsen tamago on the other hand is cooked in water that is off the boil. So both the whites and yolks come out silky and custard like. Both eggs are considered soft cooked or soft boiled.