Preheat oven to 350 degrees. Line cookie sheets with parchment paper.
In a large bowl whisk together the flour, baking powder, baking soda, salt, and spices.
Add in the oats. Stir to mix together.
In another mixing bowl, add in the butter, beating with the electric mixer until it is light and fluffy. Continue beating as you add in both sugars. Beat for 2 minutes. (Or until fluffy)
Add the pumpkin, egg yolk, and vanilla. Mix until well combined.
Slowly add the flour mixture. Mix until just combined.
To form the cookies use a cookie scoop. Scoop cookie dough and roll it into a perfect ball with your hands.
Put the cookie balls (2 inches apart) on the cookie sheet.
Flatten the cookie balls into flat cookies using 2 fingers.
Bake at 350 degrees for 9-10 minutes. (Or until the cookie edges turn golden brown)
When the cookies are done take out of the oven, allowing them to cool for 5 minutes before transferring to a cooling rack.
Filling Instructions
In a medium-sized mixing bowl, beat the butter until light and fluffy (about 3 mins).
Slowly add in powdered sugar and salt to the butter mixing on low speed.
Still mixing on low speed, add the heavy cream and vanilla continuing to beat until all of the ingredients are mixed. Increase the speed on the mixer to medium-high for 2 more minutes. (Or until light and fluffy)
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Put the frosting into a large frosting bag fitted with a large round tip. Slowly squeeze the filling onto one half (or the top cookie) of the cookie. Add the other half of the cookie on top of the bottom half with frosting.
