01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Whisk flour, baking powder, baking soda, and fine sea salt in a medium bowl.
03 - Beat butter, granulated sugar, and brown sugar until light and fluffy, approximately 2-3 minutes.
04 - Mix in egg and vanilla extract until fully incorporated.
05 - Gradually add dry ingredients to wet mixture, mixing until just combined.
06 - Gently fold chopped pistachios into dough.
07 - Drop tablespoon-sized mounds onto prepared sheets, spacing 2 inches apart.
08 - Press each mound lightly and sprinkle with flaky sea salt.
09 - Bake 11-13 minutes until edges turn golden while centers remain soft.
10 - Rest cookies on baking sheet 5 minutes, then transfer to wire rack.