Heat butter in a light-colored saucepan over medium heat, stirring constantly until brown specks appear and the aroma is nutty; transfer to a bowl to cool completely.

Spread pumpkin puree on a layer of paper towels and blot firmly with more towels until excess moisture is absorbed and volume is reduced by half.

Whisk the cooled brown butter with granulated sugar and brown sugar until smooth.

Incorporate the blotted pumpkin, egg yolk, and vanilla extract into the butter mixture.

In a separate bowl, whisk together flour, baking soda, salt, and pumpkin pie spice.

Fold the dry ingredients into the wet ingredients until just combined, ensuring no dry pockets remain.

Chill the dough in the refrigerator for 60 minutes to prevent spreading.

Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.

Scoop 1.5-tablespoon sized balls of dough and place them 2 inches apart on the prepared sheets.

Bake for 10 to 12 minutes until the edges are lightly browned; cool completely on a wire rack.

Melt white chocolate wafers in 30-second intervals in the microwave until smooth.

Spoon a dollop of white chocolate onto each cookie, using a spoon or toothpick to drag the bottom downward into a ghost tail shape.

Apply two mini chocolate chips to the wet chocolate to create the ghost's eyes.