Cream butter and sugars together until light and fluffy. Stir in egg, vanilla and molasses. Whip 1-2 minutes or until it turns a light brown color. Stir in remaining ingredients and mix until dry ingredients are just combined.
Scoop a 2 teaspoon ball of dough into your hands and roll. Coat in granulated sugar. Place on silicone baking mat, lightly greased cookie sheet or parchment paper lined cookie sheet.
Bake 6-7 minutes or until outside looks cooked but inside is still soft and gooey. Cool 5 minutes on cookie sheet before transferring to cooling rack.
For the cinnamon buttercream: mix butter, sugar, vanilla cream and cinnamon together until a thick and smooth frosting forms. 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 OR store in an airtight container for up to three days.