Preheat oven to 350 degrees F and line two baking sheets with parchment or silicone.
With an electric mixer, cream butter, sugar, brown sugar, baking soda, and baking powder until fluffy.
Add egg and vanilla, and mix again until homogenous.
Add flour and mix slowly until the dry ingredients are just combined.
Add mochi and white chocolate chips and mix again until evenly combined.
Divide cookie dough into 13 balls, each about the size of a golf ball, and divide among the two baking sheets.
Add additional mochi bits and the konpeito candies on top of the cookie balls for decoration, pressing them into the dough.
Bake each tray of cookies for 15 minutes or until lightly browned at the bottom, no chilling required.
Cookies keep well in an airtight container at room temperature.