10~ 15 minutes. Chestnut cooking is mainly to fully heat the starch and cellulose in chestnut nuts to make chestnuts fragrant and soft. Put cold water into the pot and turn on the fire. After the water boils, turn to low heat and continue to cook. 10 minutes later, chestnuts can be cooked thoroughly. If there are many chestnuts or chestnuts are big, you can boil chestnuts for 15 minutes or longer.