Add mochiko flour, sugar, matcha, and water into a shallow microwave-safe bowl. Stir to combine. Cover with a lid.
Microwave in 1-minute intervals, stopping after each minute to stir. Repeat for another 1-2 minutes, for a total for 2-3 minutes total cook time (depending on the power of your microwave). Cooked mochi dough will be translucent.
Stir with a silicone spatula and divide into 4 equal portions.
Liberally dust a silicone mat with a little kinako soy bean powder or koh fun.
Take one portion of mochi dough and place it onto the mat. Use a spatula to flatten it into a round circle. (Carefully use your fingers dipped in water to help flatten).
Place a red bean filling on top of the mochi dough and pinch to seal the edges. Gently shape the mochi so it's round and dust with kinako soy bean powder.
Place the mochi seam-side down onto a muffin liner.
Repeat with the remainder.
Notes
Mochi is best enjoyed on the same day it is made. Do not refrigerate mochi.