In a stand mixer, beat the butter and 1 cup sugar on medium speed for about 3 minutes, until light and fluffy. Add the egg and vanilla, beat for another minute. Add the pumpkin and beat until combined.
In a separate medium sized bowl, whisk together the flour, pumpkin pie spice, 1/2 teaspoon cinnamon, salt, baking powder, baking soda. Turn the mixer to a low speed and add the dry ingredients slowly. Mix until just combined.
Cover the bowl with plastic wrap and refrigerate cookie dough for one hour.
Preheat oven to 350 degrees F.
In a small bowl, combine the 4 tablespoons of sugar and then 2 tablespoons of cinnamon. Form the cookie dough into 1 1/2 inch balls and roll in the cinnamon/sugar mixture.
Place cookie dough balls 2 inches apart on a cookie sheet.
Bake for 12 minutes. Let cool for 5 minutes, then transfer to a wire rack.
In a stand mixer, use your whisk attachment and beat all filling ingredients on medium speed for about 2 minutes or until light and fluffy.
Spoon dollops of the cream filling onto the underside of the cooled cookies and top with another cookie. Repeat until all cookies are sandwiched together. Store in tightly covered container.