Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
Whisk dry ingredients – In a bowl, sift flour, matcha powder, baking powder, and salt. Set aside.
Cream butter & sugar – Beat softened butter and sugar until light and fluffy (2-3 mins).
Add wet ingredients – Mix in egg yolk and vanilla until combined.
Combine dry & wet – Gradually fold dry ingredients into the butter mixture until a dough forms.
Fold in chocolate chips (if using).
Shape cookies – Scoop 1-tbsp portions, roll into balls, and flatten slightly on the baking sheet.
Bake for 8-10 mins (edges should be lightly golden).
Cool on the sheet for 5 mins, then transfer to a wire rack.
