Melt butter in a saucepan over low heat. Allow to cool to room temperature.

In a mixing bowl, combine cooled butter with granulated sugar until smooth. Add egg and vanilla extract, mix well.

In a separate bowl, whisk together flour, baking powder, baking soda, matcha powder, and salt. Fold into wet mixture until just combined.

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

Preheat oven to 180ºC (355ºF). Prepare a lined baking sheet.

Place chilled cookie dough on the baking sheet, leaving space between each. Bake for 10-11 minutes until set and slightly golden.

Allow cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

Whip together mascarpone, confectioners sugar, heavy cream, and vanilla until stiff peaks form. Pipe onto cooled cookies.

Dust with matcha powder before serving.