Preheat oven: Set oven to 350°F (175°C). Line baking sheets with parchment paper.
Mix dry ingredients: In a medium bowl, whisk flour, baking powder, baking soda, cinnamon, nutmeg, and salt. Set aside.
Cream butter and sugars: In a large bowl, beat butter, granulated sugar, and brown sugar until light and fluffy. Add pumpkin puree, egg, and vanilla extract. Mix until smooth.
Combine dough: Gradually add dry ingredients into wet ingredients, mixing until just combined. Fold in white chocolate chips.
Shape cookies: Scoop dough with a tablespoon or cookie scoop and place onto prepared baking sheets, spacing about 2 inches apart.
Bake: Bake for 10–12 minutes, until edges are lightly golden and centers are set. Let cookies cool on the sheet for 2 minutes before transferring to a wire rack.
Serve: Enjoy warm with milk, or store for later.