- Peel the sweet potatoes, chop into small chunks and soak it in a bowl of water for 2-3 hrs.
- Boil it in a pot of water until it becomes soft.
- While the sweet potato is still soft, strain it through a sifter to make it into a puree.
- Mix the sugar, syrup and mirin in a saucepan and cook over low heat until it starts to simmer.
- Turn the heat off, add pureed sweet potato and mix them well together.
- After mixing it well, cook over low heat for 15 mins. Keep stirring to avoid mixture from sticking to the bottom.
- Turn off the heat, add the chestnuts and cover them with the pureed sweet potato mixture. Serve cool.