Soak azuki beans for 6-8 hours or overnight. Rinse under cold water and drain.
Add beans to a pot along with 4 cups of water and bring to a boil.
Lower heat to a simmer, cover and cook for 1 hour or until beans are soft enough that you can easily squash them between your fingers.
Drain well and return beans to the pot.
Add sugar and salt and turn the heat on to medium high. Stir constantly for 7-10 minutes and occasionally mash the beans against the side of the pot until the mixture turns into a paste.
Turn the heat off and transfer the paste into a bowl. Cool to room temperature before using.
You can reduce the amount of sugar by up to 1/4 cup if you prefer a paste that’s less sweet.