What you will need:Whoopie Cookies1 1/2 cups butter or neutral oil1 cup dark brown sugar1/2 cup granulated sugar1 large egg2 tsp vanilla extract1 tsp dark molasses1 1/2 cups all purpose flour1 tsp baking soda1/2 tsp salt1/4 tsp ground cinnamon3 cup instant oats
Filling3/4 cup butter1 tsp vanilla extract2 1/2 cups powdered sugar1 tbsp milk
Directions:Cream butter, brown sugar, and granulated sugar in a stand mixer with paddle attachment for a couple of minutes. Slowly beat in the egg, vanilla, and molasses and mix until smooth.
Mix in the baking soda, salt, and cinnamon. Add in the flour and oats and mix on low speed until combined.
Scoop the dough using a 4 tsp cookie scoop to portion the dough onto a parchment or silicone mat lines baking sheet and space about 2" apart. Flatten the balls slightly and place in the fridge for about 20 minutes.
While the cookies chill, preheat the oven to 375°F and make the filling.Cream the butter in a mixer with a paddle attachment until fluffy, about 5 minutes and then beat in the vanilla. Slowly add powdered sugar, about 1/2 cup at a time. Once all of the powdered sugar is combined, beat in the milk. Mix on high for a few minutes until fluffy and combined.
Add the filling to a ziploc bag {I place in a glass so it's easy to fill} and put in the fridge to firm up.
Bake the cookies 10-12 minutes, until lightly golden brown. Let the cookies cool on a rack for 30 minutes before filling.
Snip the corner of the filling bag and fill half the cookies {with the bottom facing up.} 
Place the second cookie on top for a sandwich!
Enjoy!
