According to the information from KyushuDrunkDining.com, you can start by heating the chassis of the mold. By heating the chassis, you can make the custard separate from the bottom of the mold, or even make the custard partially melt where it contacts the inner wall of the mold, so that the custard can be easily dislodged from the mold, and then you can take out the custard in the mold.