Peel the skin of the sweet potato and take off sprouts carefully with a knife.
Grate 1/4 of the sweet potato with a grater.
Cut the rest of the sweet potato into large chunks. Place in a saucepan with salted water, bring the water to a boil, then boil for about 10 minutes.
Mash the boiled sweet potato as finely as possible, using something like a fork.
Add the grated sweet potato from Step 2 and about 100 ml of water to the pan. Continue mixing while heating over low heat.
When it becomes transparent after about 5 minutes, add sugar and simmer until it's reduced by about half.
Then, add the sweet potato from Step 4 and mix well.
Put the dough in a pound cake pan covered with plastic wrap, then cover the top with the wrap. If you press it down with another pound cake pan, the shape will flatten out
This makes great use of the sweet potato taste. My friend says that it is even better than the one from Funawa!?
Story Behind this Recipe
I couldn't forget the taste of yokan from a confectionery called Funawa, which I received from a friend from Tokyo. According to the ingredients list, all that was in it was sweet potato and sugar. I figured out how to make it firm by trial and error, and this is the result.
You can't beat "Naruto Kintoki" variety sweet potoatoes for this!