Melt butter in a small saucepan over low heat until fully melted, about 3-5 minutes. Remove from heat and let cool.

In a mixing bowl, combine the cooled melted butter and granulated sugar, whisking until creamy. Add egg and vanilla extract, beating until smooth.

In a separate bowl, whisk together flour, baking powder, baking soda, matcha powder, and salt until mixed.

Gently fold the dry ingredients into the wet mixture, stirring until just combined. Aim for a vibrant green color.

Scoop dough into balls, place on a baking sheet lined with parchment, flatten slightly, and chill for 30 minutes.

Preheat oven to 180°C (355°F) while dough chills.

Bake cookies for 10-11 minutes until edges are set and centers remain soft.

Remove cookies and let cool on the baking tray for about 3 minutes before transferring to a wire rack.

Whip together mascarpone, vanilla extract, confectioners' sugar, and heavy cream until stiff peaks form.

Once cookies cool, pipe mascarpone cream onto each cookie and dust with matcha powder.