Preheat the oven to 350°F (convection). Line a baking sheet with parchment paper and set aside.

In a large bowl or stand mixer fitted with the whisk or paddle attachment, beat the room-temperature butter and granulated sugar until light and off-white in color, about 1–2 minutes.

Add the egg and vanilla extract, mixing until fully combined.

Add the all-purpose flour, matcha powder, baking powder, and baking soda. Gently fold the dry ingredients into the dough until no dry spots remain.

Scoop ⅓ cup portions of cookie dough and place onto the prepared baking sheet, spacing evenly apart.

Bake for 11–12 minutes, until the edges are set and the centers look slightly underbaked.

For perfectly round cookies, use a round bowl, cup, or cookie cutter to gently swirl around the cookies immediately after removing them from the oven.

Let the cookies rest on the baking sheet for about 10 minutes before transferring.

Beat the butter until light and off-white. Add the powdered sugar and mix until fully incorporated and slightly thick.

Add the heavy cream and vanilla extract, then whip until light and fluffy.

Pipe or spread the frosting onto the cooled cookies in a swirl design.

(Optional: sprinkle with extra matcha powder on top.)

Enjoy fresh, or store cookies in an airtight container in the refrigerator for up to 8 days.