15-20 minutes. If the water doesn't reach the taro, bring it to a boil and cook for 15-20 minutes. You can poke it with chopsticks. If it's cooked, it's easy to poke through. If you want to steam it worse, you can put more water for a while. If steamed in a pressure cooker, it takes more than 20 minutes for large taro and 15 minutes for small taro.