Step 1

Mix mochiko, sugar, and ⅓ cup plus 2 Tbsp. cold water in a small bowl. Cover with foil. Bring 2" of water to a simmer in a large pot. Fit with steamer basket; add bowl to basket. Cover pot with a tight-fitting lid. Steam until mixture is translucent and gummy, 20–22 minutes. Remove bowl and stir mixture until a thick, smooth, slightly sticky dough forms.

Step 2

Meanwhile, schmear strawberries all over with bean paste, if using.

Step 3

Sprinkle a surface lightly with potato starch; turn out mochi on top. Dust with more starch; cut into 8 pieces. Stretch a piece of mochi around a strawberry to encase; pinch together to close. Roll between your palms to smooth; brush off excess starch. Repeat with remaining mochi and strawberries.

Step 4

Do Ahead: Strawberries can be wrapped in mochi 4 hours ahead. Store tightly covered at room temperature.