Authentic Tsubu-an (Chunky Azuki Bean Paste) Delicious Made from Scratch!
This takes about 2 hours from start to finish. It's worth taking the time to make this. Anko (or sweet red bean paste) is the foundation of wagashi (traditional Japanese confectionery). If you use good-quality anko, all of the sweets you make will be better.
Rinse the adzuki beans in the same way you rinse rice. Put the beans in a pot with 1.5 liters of water, and bring to a boil over high heat.
Keep cooking over high heat after it comes to a boil. The beans will start to absorb the water and the skins will become wrinkled.
Cook for 20 minutes. When the skins become smooth again (an indication that they've become saturated), drain the beans and throw away the cooking water.
Put the beans back in the pan with 1 liter of water, and bring to a boil over high heat again. Cook the beans for 10 minutes or so. When the beans start to split open, turn the heat down to low (to the point where the water is just barely bubbling).
If the water level drops, add boiling water so that the beans are covered. Simmer over low heat for about 30 minutes until all the beans have split and are tender. Take the pot off the heat.
Add cold water to the pot in a thin stream, letting it overflow. Keep running cold water into the pot until the beans are cool and the water in the pot is more or less clear.
When the beans have cooled down, drain the water.
Return the adzuki beans to the pot, add sugar and salt, and turn the heat on to medium (if you use granulated sugar instead of castor (superfine) sugar, it will taste sharper).
By the time the pot comes to a boil, water will have come out of the beans. Keep simmering while stirring to evaporate the water.
Stir by scraping across the bottom of the pot. When you can clearly see the bottom, mash the beans up with the spatula as you mix it into a paste.
Turn the heat off just before it reaches your desired consistency. Keep stirring to let the residual heat evaporate the moisture. Let it cool down, and it's done.
The bean paste can be stored wrapped airtight with plastic wrap in the refrigerator for about a week. Use it up before it loses its flavor and fragrance.
A recipe using homemade tsubu-an: Recipe ID: 2116539, Zenzai (warm tsubu-an with mochi rice cake).
A recipe using homemade tsubu-an: Recipe ID: 2127156, Amazake dorayaki (small pancakes filled with tsubuan; the dough has amazake sweet fermented rice malt).
A recipe using homemade tsubu-an: Recipe ID: 2161371, Kneaded Yokan (thick bean jelly); authentic but easy.
Story Behind this Recipe
I watched my grandmother make it and tried to copy her. I read about the cooling method described in step 6 on the website of a traditional Japanese confectioner called Kanshundo. I think they do it this way to get rid of bitterness and to firm up the cooked azuki beans. I incorporated it into my recipe.
There's no need to pre-soak the azuki beans before cooking. They have such thick skins that cold water doesn't penetrate them easily, and if you don't soak them properly, it may even lead to uneven cooking. Cook the beans over medium heat for the 2nd half. It won't burn, but it does cook fast once you can mash it into a paste, so watch carefully for the right time to take it off the heat.