Rinse the adzuki beans and put into the inner pot of a thermal cooker.
Add enough water to equal about 3 times the volume of the adzuki beans. Cover with the lid and boil for 5 minutes. Then place the inner pot into the outer pot and leave it like that for at least 4 hours. (The photo shows the beans boiling)
The azuki beans are done when you they're soft enough to mash when you squeeze one with your fingers.
Add the contents of the pot, including the liquid, to a blender. Blend for about 10 seconds. (Skip this step if you do not have a blender.)
Pass the adzuki beans through a strainer. If they're difficult to strain, pour some water over the beans. Continue to add water until the bean pieces are all covered with water.
After the azuki beans are strained, let them sit a little while. A layer of water will form on top of the beans. Carefully discard the top layer of water.
Line a strainer with cheesecloth or a dish towel with a fine weave and strain the bean paste.
Squeeze the cheesecloth or dish towel to strain out the water.
Put the anko in a saucepan and add 1/3 of the sugar. Place the saucepan over low heat and mix with a wooden spatula, stirring from the bottom of the pot.
When the anko starts to soften, add 1/2 of the remaining sugar while continuing to heat over low heat. Wait a little while and then add the rest of the sugar.
Keep mashing with the wooden spatula until the spatula leaves a ribbon in the bean paste. Add a pinch of salt and transfer to a tray or other container to cool.
(Extra tip) This anko is not very sweet, so it only keeps in the refrigerator for about 1 week. It's very convenient if you divide it up into easy-to-use portions and freeze them.
Story Behind this Recipe
I challenged myself to make delicious anko for my husband, who loves wagashi. After many attempts, I came up with this easy and delicious recipe. I have shared other recipes that you can use this anko with too.
Using a blender in step 5 makes the work a lot easier. Recipe Variations: Anpanman Bread, Recipe ID: 1082367. Strawberry Daifuku, Recipe ID: 1093846