Firm Traditional Sweet Red Bean Jelly

Prepare a rectangular mold (e.g., loaf pan) by lining it with plastic wrap or parchment paper, ensuring overhang for easy removal.

In a medium saucepan, sprinkle the agar-agar powder evenly over the water and let it hydrate for 5 minutes.

Heat the saucepan over medium heat, stirring constantly, until the agar-agar powder is completely dissolved. Bring it to a gentle boil for 1-2 minutes to ensure full dissolution.

Reduce heat to low. Add the smooth red bean paste (koshian), granulated sugar, and salt to the saucepan. Stir continuously with a spatula, breaking up the paste until it is fully incorporated and the mixture is smooth and thick, about 5-7 minutes. Ensure the sugar is completely dissolved.

Carefully pour the hot mixture into the prepared mold.

Gently tap the mold on the counter a few times to release any trapped air bubbles, creating a smooth surface.

Let it cool at room temperature for about 30 minutes, then transfer it to the refrigerator to chill and firm up for at least 2 hours, or until completely set.

Once firm, invert the yokan onto a cutting board, remove the lining, and slice into desired portions (e.g., 1 cm thick rectangles) using a wet knife for clean cuts.