Sift together flour, matcha powder, baking soda, and salt in a medium bowl. Set aside.
Cream butter and sugar until light and fluffy (3-4 minutes).
Beat in egg and vanilla until well combined.
Gradually mix in dry ingredients until just combined.
Fold in white chocolate chips.
Chill dough for 30 minutes.
Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
Roll dough into 1-inch balls, place 2 inches apart.
Press extra chips on top if desired.
Bake 10-12 minutes until edges are set but centers still soft.
Cool on baking sheet 5 minutes before transferring to wire rack.