'- 200 g Azuki beans (7 oz; A little bit less than 1 cup)- Water- 175-200 g sugar (¾ - 1 cup)- ½ tsp kosher/sea salt (I use Diamond Crystal; Use half for table salt)

1. Gather all the ingredients.2. Rinse azuki beans and discard broken ones.3. Transfer the drained azuki beans to a large pot. Add water till 1-2 inches above azuki beans. Turn the heat on high.4. Bring the water to boil over medium high heat.5. Once boiling, discard the water and put the azuki beans back into the same pot.6. Add water till 1-2 inches above azuki beans.7. Bring the water to a boil over medium-high heat. Once boiling, put an otoshibuta (drop lid) over the azuki beans (Otoshibuta will prevent the beans from dancing around too much). Turn down the heat to medium-low and keep it simmering for the next 1 to 1.5 hours.8. Water will evaporate so you need to keep adding water so the beans are submerged. After 1 hour, pick one bean and mash it with your fingers. If it is mashed easily, it's done.To Make Tsubuan (Chunky Red Bean Paste)1. Drain the azuki beans over a sieve.2. Put the beans in the same pot. Turn the heat to medium-low heat and add half of the sugar.3. Mix well with the azuki beans. Once sugar is dissolved, add the rest of the sugar.4. Mix, stirring constantly and add the salt.5. If you plan to use red bean for Zenzai (Oshiruko), you can use it right away. If you prefer a thicker version, reduce the soup.6. Let the moisture evaporate. When you can draw a line on the bottom of the pot, turn off the heat. Don't worry if it's still loose; Anko will continue to thicken as it cools. Transfer to a flat baking sheet to let cool completely. Tsubuan is ready to use. Scroll down to see how to store it.To Make Koshian (Fine Red Bean Paste)1. Drain the azuki beans over a sieve, reserving some cooking liquid.2. Transfer the beans to a food processor. Add 1-2 Tbsp cooking liquid if necessary and run the food processor until the beans become a fine paste.3. Transfer the fine paste back into the same pot. Turn the heat to medium-low heat and add half of the sugar.4. Mix well with the bean paste. Once sugar is dissolved, add the rest of the sugar.5. Let the moisture evaporate, stirring constantly. Add the salt.6. When you can draw a line on the bottom of the pot, turn off the heat. Don't worry if it's still loose; Anko will continue to thicken as it cools. Transfer to a flat baking sheet to let cool completely. Koshian is ready to use.