If using anko powder: Heat 2/3 cup of water and 1/2 cup of sugar in a small pot. Add 1/4 cup of anko powder and stir well. Cool the anko filling. Make 12 small anko balls and set aside.
If using sweetened red mung beans: Put the beans in a strainer and rinse it once with running water; drain well. Transfer to a food processor or blender and blend until fine or use a potato masher or ricer. Divide it into 12 and form it into balls and set aside.
Put glutinous rice in a big bowl. Combine coconut milk, sugar and extract (if using), in a bowl or measuring cup, pour over glutinuous rice and mix until smooth- make sure it's completely free of lumps.
Cover with cling wrap and put inside the steamer. Steam for about 20 minutes.
Dust a clean work surface with some potato starch, dust hands with some potato starch too. Remove the hot mochi from the bowl to the pan onto the dusted surface. The mochi is hot and sticky, so please be careful not to burn your hands.
Dust hands with more potato starch and divide the mochi into 10-12 pieces by hands.
Make 10-12 flat and round mochi. Put a piece of filling on a mochi and wrap the anko by stretching mochi. Form each into a ball and round the daifuku. Repeat the process to make more pieces. Enjoy! :)