I used oofuku-mame this time. Take the oofuku-mame out of the bag, rinse well in plenty of water to clean them, and remove any beans eaten by insects.
Soak the oofuku-mame in fresh water overnight. In summer, it's preferable to change the water in the middle.
The oofuku-mame will about triple in size overnight.
Drain the oofuku-mame, transfer to a small sauce pan, add plenty of fresh water, and cook over strong heat.
Once it has come to a boil, bring down to low heat, and cook for 5 minutes.
Turn off heat and let steam for 5 minutes with a lid on.
Drain the oofuku-mame and soak in fresh water. Prepare another bowl of fresh water.
Peel the oofuku-mame skins. An easy way of removing skins is to squeeze the beans from the back toward the indent. The bean will pop out from the indent. Soak the peeled beans in water.
Drain the peeled beans, transfer to a small sauce pan, add plenty of fresh water, and cook over strong heat.
Once it comes to a boil, skim off the scum carefully.
Turn down the heat to low and boil until tender (don't cover with a lid). The cooking time is depending on the condition of beans, but about 1.5 hours.
After the beans are tender, carefully mash with a wooden spatula etc., and pass through a strainer while wetting with water.
Leave for a few minutes, and skim the top layer of water with a ladle carefully.
Pass the beans through a strainer in water by gently stroking the beans with your hand. (The beans will pass through easily this time, so you don't need to use the wooden spatula).
Repeat Step 14 three times.
Pass the beans through a bleached cotton cloth, and wring out tightly.
Transfer the beans to a small sauce pan, add the sugar, and mix well with the wooden spatula.
Keep mixing until the sugar is dissolved and the paste is quite watery.
Knead the paste in one direction on medium heat. The cooking time depends on the heat and how watery the paste is. It is usually about 5 to 10 minutes. Be careful not to burn it.
Professional chefs usually use 'bozu-nabe' (a lightweight hammered pot, made of copper) etc. You can also use 'yukihira-nabe' (a lightweight hammered pot, made of aluminum) but be careful not to burn the paste.
The paste is ready when it falls and forms a mound when lifted with the wooden spatula. Turn off the heat.
Line a tray with plastic wrap or a moistened cotton cloth. Divide the paste into small portions, place them on the tray, and cool them down.
When the paste has cooled, it's done.
Story Behind this Recipe
I made this recipe for those who cannot buy shiro-an at store easily.
The basic nerikiri recipe by using this shiro-an is (Recipe ID: 2253702).
I used oofuku-mame. If you use smaller beans such as tebou-mame, refer to the recipe for koshian' (small red bean paste). The taste of shiro-an differs more clearly depending on the condition and sweetness of beans than the variety of beans. I didn't use much sugar because of the intended use of the shiro-an.