Preheat oven to 350 degrees F. Line a baking sheet with parchment paper.
In a mixing bowl, add in the butter, brown sugar and granulated sugar. Beat until light and fluffy (about 2 minutes). Scrape down the sides.
Add in the egg and maple extract. Beat on medium until incorporated. Scrape down the sides of the bowl.
Add in the old fashioned oats and beat until combined.
Add in the flour, baking powder and salt. Mix until combined.
Scoop out cookies using a large 2 tablespoon cookie scoop and place on prepared pan. Press the cookies down so they're no longer domed.
Place in the preheated oven and let them bake for 10 to 11 minutes until the edges are golden brown.
Let the cookies cool for 10 minutes before moving them to the cooling rack.
Once the cookies are completely cooled, add the frosting to a piping back and cut off a corner. Pipe a nice large mound and add the top cookie to the oatmeal maple cream pie.
Frosting
Add the butter, maple extract and creamer to a large mixing bowl. Mix with a hand mixer until incorporated.
Add the powdered sugar and mix on low until almost completely incorporated. Turn the mixer on high and beat for another 2 - 3 minutes until the frosting becomes light in color and texture.