Mizu Yokan

1. Gather all the ingredients. I use a nagashikan (6 x 5 x 2 inches or 15 x 13.5 x 4.5 cm). If you do not use a nagashikan, you might want to use plastic wrap to line your mold for easy removal later on.
2. To a small saucepan, add 1½ cups water. Then, add 4 g kanten (agar) powder. Whisk well and bring to a boil.
3. Once boiling, lower the heat. Whisk and let the powdered kanten dissolve completely, about 2 minutes.
4. Add 14 oz sweet red bean paste (anko) and dissolve the koshian paste with a silicone spatula.
5. Once the red bean paste has completely dissolved, add ⅛ tsp Diamond Crystal kosher salt. Remove from the heat to let it cool a bit, about 2–3 minutes.
6. Pour some of the red bean mixture into the mold until the bottom of the nagashikan is covered, about ¼ inch (0.6 cm) deep. Then, let it cool at room temperature until it has set, about 10 minutes (the time varies depending on the temperature of your kitchen).
7. Once solidified, place the chestnuts from 1 jar kuri kanroni (chestnuts in heavy syrup) on top, spacing them evenly apart from each other.
8. Pour the rest of red bean mixture over so that it covers the chestnuts. Let it cool on the counter for about 15 minutes to set. Then, wrap and transfer to the refrigerator until it has completely chilled, about 2 hours.

To Serve

1. Remove from the refrigerator. Run a knife along the edges of the nagashikan and lift the inner removable tray. Slide the yokan out of the inner tray onto a cutting board.
2. Cut the yokan into 3 rectangular bars, then slice each bar into pieces ½–1 inch (1.3–2.5 cm) thick. Serve chilled.

To Store

1. You can wrap and store the Mizu Yokan in an airtight container and keep it in the refrigerator for 3 days.