Step 1

Make the red bean filling: In a medium bowl, stir together the red bean paste, sweetened condensed milk, and sugar until well combined. Weigh out 10 15-gram (about 2-teaspoon) portions of the mixture and roll into balls between the palms of your hands. If the mixture is sticky, wet your hands with water before rolling. Transfer the balls to a plate and cover with plastic wrap. Refrigerate while you make the tangyuan skin.

Step 2

In a medium bowl, combine ½ cup of the mochiko flour and ¼ cup of warm water. Mix with chopsticks until all the water is absorbed and the flour starts to clump. Mix in the remaining ¼ cup warm water until a smooth, thick paste forms. Mix in the remaining ½ cup mochiko flour until a dough forms. Knead until the dough becomes soft and pliable, like molding clay. It should be somewhat tacky, but not so much that it sticks to your hands.

Step 3

Bring a large pot of water to a boil. Line a plate or baking sheet with parchment paper.

Step 4

Roll the tangyuan dough into 10 22-gram (about 1-tablespoon) balls. Flatten each ball into a 1½–2-inch wide disc that is about ¼-inch thick. Place a red bean ball in the center of each tangyuan skin and carefully wrap, pinching closed. Roll between your palms to create a smooth ball. Repeat with the remaining red bean paste balls and tangyuan skins.

Step 5

Drop the tangyuan into the boiling water and cook for 6–7 minutes, until floating. Once the balls float, cook for 1 more minute before removing from the water. Transfer the cooked tangyuan to the prepared plate and freeze for 1 hour, or until hardened.

Step 6

Make the matcha cookie dough: In a medium bowl, combine the butter, sugar, and egg. With a whisk or electric hand mixer, mix until well combined and fluffy. Whisk in the vanilla. Sift in 1 cup (120 grams) of flour, the baking powder, and matcha powder. Fold the dry ingredients into the wet ingredients until just combined. Sift in the remaining ½ cup (60 grams) of flour and mix until thoroughly combined with no dry spots. Cover and refrigerate for 30 minutes.

Step 7

Preheat the oven to 350°F (180°C). Line a baking sheet with parchment paper.

Step 8

Remove the cookie dough from the refrigerator and portion into 10 40-gram (about 2-tablespoon) pieces. Roll each piece into a ball and create a well in the center. Place a frozen tangyuan into each well and carefully cover with the cookie dough, then roll into smooth balls. Place on the prepared baking sheet.

Step 9

Bake the cookies for 15 minutes, then reduce the oven temperature to 300°F (150°C) and bake for another 5 minutes, until the cookie dough is set and lightly golden brown on the bottom.

Step 10

Let the cookies cool for 10 minutes before serving.

Step 11

Enjoy!