Step 1

Transfer the mung bean into a large bowl and fill with cold water. Wash the beans by swirling in the water and then pouring out the rinse water. Repeat this process 2 more times or until the water is mostly clear. Fill the bowl with cold water and let the beans soak for at least 2 hours.

Step 2

Wash the beans one more time. Drain using a colander. Transfer the beans into a rice cooker. Add the salt and water. Spread out the beans into an even layer. Close the lid and cook using a basic white rice setting.

Step 3

Transfer the cooked beans into a medium bowl. Add the sugar, vanilla sugar and vegetable oil. Using a paddle spoon, mash the beans while still hot.

Step 4

Use a medium cookie scoop to transfer small filling mounds onto a plate, making a total of 10 mounds. Roll the filling mounds between your palms forming a rough ball. After all filling balls are made, cover with plastic wrap to keep from drying.

Step 5

Remove the potato skin using a vegetable peeler. Dice the potato. Transfer the potatoes into a small saucepan. Add 1/2 cup water. Cover and cook the potatoes over Medium heat until soft. Mash the potatoes using a spatula or spoon.

Step 6

Combine the 1 cup boiling water and sugar in a measuring cup.

Step 7

In the bowl of a stand mixer, add the glutinous rice flour, rice flour and baking powder. Mix on Low speed for 15 seconds. Add 1/3 cup mashed potatoes (prepared earlier) and the vegetable oil. While mixing on Low speed, gradually add the water and sugar mixture until a dough forms. (This takes approximately 2 minutes.) Cover the dough and let rest for 30 minutes.

Step 8

After the resting period, mix on Low speed for 30 seconds. Cover the dough with plastic wrap or a kitchen towel to prevent drying.

Step 9

Use a medium cookie scoop to pick up a small mound of dough. Flatten the dough between your palms. Using your fingers, flatten the edges, making a circle about 3 inches in diameter. Place a mung bean filling ball in the center of the dough circle and wrap the dough around the filling. Pinch the dough together covering the filling completely. Roll between your palms to form a smooth ball. Leave the donuts round or flatten into a small patty.

Step 10

Transfer the donut to a large plate and cover with a damp towel. Continue with the same steps until all the mung-bean filled donuts are made.

Step 11

For the remaining dough, use a medium cookie scoop to transfer small mounds onto a plate. Roll each mound into a rope about 5 inches long. Join the ends together making a ring. Continue making the donut rings using the remaining dough.

Step 12

In a large wok, add the vegetable oil. Heat the oil over Low heat until the temperature is approximately 265-270 F (130-132 C). Carefully transfer the donuts rings into the oil. Separate the donuts so they don't stick together.

Step 13

When the donuts float to the top, flip them over. For the first 5-6 minutes, flip the donuts every 1 minute so they puff up evenly on both sides.

Step 14

Increase the heat to Medium and fry the donuts until they are golden.

Step 15

Transfer the donuts to a plate lined with paper towels. Blot off the excess oil.

Step 16

Fry the donuts with the mung bean filling following the same steps above.

Step 17

In a small saucepan, add the sugar, vanilla sugar, water and lemon juice. Combine together and moisten the sugar.

Step 18

Heat the sugar over Medium heat. When the syrup starts to bubble vigorously, swirl in the pan a few times and return to the heat. Cook until the syrup turns a honey color, approximately 4-5 minutes. Turn off the heat. Let the syrup rest for 2-3 minutes or until it deepens in color.

Step 19

Drizzle the glaze on top of the donuts. Optionally, dip the donuts into the glaze, coating one side. Sprinkle roasted sesame seeds on top of the donuts while the glaze is still hot.

Step 20

Enjoy the donuts while they're fresh. Store any remaining donuts in a covered dish and enjoy within 1-2 days.