After the pressure cooker is boiled, cook it for 30-40 minutes, not too long. After I cooked it for 40 minutes, I quickly reduced the pressure and opened the pot. It was delicious. I wonder if it would be better if I boiled it again. It became even more crispy, so I cooked it in a pressure cooker for another 30 minutes. Now it was broken and hardened like rubber, so don't use it for too long, otherwise it will become hard.