Combine flour, baking soda, salt and cinnamon in a bowl and whisk until fully combined. Set aside.
Beat butter for 1 minute on high speed until light in color.
Add brown sugar and granulated sugar. Beat for 2 minutes on high. Scrape the bowl and beat until well combined and fluffy.
Add eggs, vanilla and molasses. Beat until incorporated. Scrape the bowl and beat again.
Slowly add the dry ingredients into the wet on low speed. Stop mixing once everything is incorporated. Scrape the bowl and beat once more.
Add the oats and mix on low until combined.
Cover and chill for thirty minutes.
Preheat oven to 350 degrees.
Using a standard ice cream scoop create scoop-size cookies. Flatten to 1/2 inch thick. Bake 8 at a time on a half-size sheet pan for 11 minutes in the middle rack. Bake in rounds.
Leave cookies on the hot sheet pan to continue cooking. Remove once cooled to room temperature.
For the filling, microwave the fluff in 10 second intervals until the cream is workable and you can easily remove it from the container. You don't want it super runny or else it will ooze out of the cookies.
Beat fluff with a pinch of salt and vanilla bean paste (you can substitute vanilla if you don't have it). Once combined put in a plastic ziploc bag and cut the tip.
Fill the middle of half of the cookies with the fluff and top with the remaining cookies.
Enjoy or store in an air tight container.