01 - Combine matcha powder, baking powder, and flour by sifting into a medium bowl.
02 - Allow butter to reach room temperature, then stir until creamy. Gradually fold in one third of the sugar at a time, mixing until smooth after each addition.
03 - Beat the egg lightly and incorporate fully into the butter-sugar mixture.
04 - Gently fold the sifted dry ingredients into the wet mixture until just combined; avoid overmixing.
05 - Fold in the semi-sweet chocolate chips evenly. Let the dough rest briefly.
06 - Roll small portions of dough between your hands into balls, arrange on a cookie sheet, and lightly flatten each.
07 - Preheat oven to 340°F (171°C). Place cookie sheet in oven and bake for 10 minutes.
08 - Reduce oven temperature to 300°F (149°C) and continue baking for an additional 10 minutes.
09 - Remove cookies from oven and transfer to a wire rack to cool completely before serving.