Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a bowl, whisk together gluten-free flour, baking soda, baking powder, salt, cinnamon, nutmeg, and ginger.
In another bowl, mix pumpkin puree, brown sugar, granulated sugar, vegetable oil, vanilla extract, and eggs until smooth.
Gradually add dry ingredients to wet ingredients, mixing until well combined.
Scoop batter onto the prepared baking sheet, forming small rounds.
Bake for 12-15 minutes until firm and slightly golden. Let them cool completely.
For the filling, beat butter, powdered sugar, vanilla extract, and milk until smooth and fluffy.
Spread or pipe filling onto one cookie and top with another to create a sandwich.
Enjoy immediately or chill in the fridge for a firmer texture.