Preheat oven to 375 F. Line a large baking sheet with parchment paper or a silicone baking mat.
Using a stand mixer or hand mixer, cream the butter and sugars together on medium-high speed until light and creamy, about 1 minute. Beat in the egg, vanilla and molasses, scraping down the sides as needed. Set aside.
In a medium bowl, whisk the flour, baking soda, salt, cinnamon, cloves and oats.
With the mixer on low speed, slowly add the dry ingredients to wet ingredients. The dough will be. Drop dough with a large cookie scoop, or make each ball of dough 2 tablespoons in size.
Bake for 10 minutes or until cookies are lightly golden around the edges. Allow the cookies to cool completely.
FOR THE FILLING
Make the filling by beating the butter, powdered sugar, cream, vanilla and marshmallow fluff until well combined.
Once the cookies are cooled, put a spoonful or small scoop of the filling on one cookie and sandwich with another. Repeat until all the sandwiches are made.