Preheat oven to 375°F. Line baking sheets with parchment paper.
Combine flour, baking soda, baking powder, and salt in a medium bowl.
Beat butter and sugar until light and fluffy (2-3 minutes). Add egg, vanilla, and sour cream, mixing until well combined.
Gradually incorporate dry ingredients into wet mixture until just combined.
Drop rounded tablespoons of dough onto prepared sheets, gently pressing to flatten.
Add sprinkles if desired.
Bake 8-10 minutes until edges set but centers remain soft.
Cool on baking sheet briefly before transferring to wire rack.
Decorate with frosting once completely cooled (optional)