01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Whisk together flour, baking powder, baking soda, and fine sea salt in a medium bowl. Set aside.
03 - Beat butter, granulated sugar, and brown sugar until light and fluffy, approximately 2-3 minutes.
04 - Incorporate egg and vanilla extract, mixing until fully combined.
05 - Gradually blend dry ingredients into wet mixture, mixing until just incorporated.
06 - Gently fold chopped pistachios into the dough.
07 - Scoop tablespoon-sized dough mounds onto prepared baking sheets, leaving 2 inches of space between each.
08 - Lightly flatten each mound and sprinkle tops with flaky sea salt.
09 - Bake 11-13 minutes until edges are lightly golden and centers remain soft.
10 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool completely.