Start by making the green layer: combine 50g rice flour, 40g sugar, 75ml water, 1-3 tbsp matcha powder in a microwave safe bowl. Mix until evenly combined and the rice flour lumps have been broken down. Place some cling film over the bowl and microwave on high for 2 minutes. The mixture will become slightly bubbly. Take care, as it will be hot, and give it a stir. Place in the microwave for 1 more minute. Give the mixture a stir again.
Add the green layer into a tray: prepare a tray, we recommended an 8 in. by 8 in. size, and lightly dust the bottom with the potato starch powder. Carefully add the green layer to the tray and stretch it out into a thin layer to coat the bottom of the tray. Using a rolling pin if needed to help spread the mocha until an even thickness is achieved.
Prepare the white and the pink layer: repeat step 1 for the remaining two layers and lay each additional layer on top of the previous one. First the white layer, then the pink layer.
Dust some potato starch powder: dust the top of the mochi with some more potato starch powder.
Cut the mochi: allow the mochi to rest for 30 minutes. Then cut with a sharp knife into diamond shapes for a traditional feel, or into squares if desired.
Serve and enjoy: enjoy with some hina arare rice crackers or some matcha tea for a sweet treat on Hina Matsuri.