In a medium bowl, using an electric hand mixer, cream butter, granulated sugar, and brown sugar together until light and fluffy.
Stir in egg, vanilla extract, and molasses. Whip 1-2 minutes or until it turns a light brown color.
Place on silicone baking mat, lightly greased cookie sheet or parchment paper lined cookie sheet.
Roll a heaping tablespoon of dough into a ball, and coat in granulated sugar.
Place on silicone baking mat, lightly greased cookie sheet or parchment paper-lined cookie sheet.
Bake 7-9 minutes or until outside looks cooked but inside is still soft and gooey.
Cool 5 minutes on cookie sheet before transferring to a cooling rack.
for the filling-
In a small bowl, using an electric hand mixer, mix butter, sugar, vanilla extract, heavy cream and cinnamon together until a thick and smooth frosting forms.
put it all together-
Spread 1/2 to 1 tablespoon of buttercream onto one cookie. Top with another cookie and place onto serving platter.
Repeat with remaining cookies. Serve immediately or store in an airtight container for up to three days.