• Preheat oven to 350 F. In a medium saucepan, bring the apple cider to a boil over medium high heat. Reduce heat to medium and simmer until cider is reduced down to 1/4 cup. This will take about 30-35 minutes. Set aside to cool before using. Line two baking sheets with parchment paper. 
• In a medium sized bowl, sift together the flour, baking powder, baking soda, salt and spices.
• In a large bowl or the bowl of an electric mixer, beat 6 tablespoons of the butter with the sugars, on medium speed until combined. Scrape down the sides of the bowl and add the vanilla followed by the eggs. Add the apple cider followed by the apple butter or applesauce. Turn the mixer on low and mix in the flour until just combined. 
• Turn the cookies out into mounds about 1 1/2 tablespoons each, placing them 3 inches apart on the baking sheet. Rotate the pan halfway and bake 11-13 minutes or until cookies spring back when touched lightly with your fingertip. 
• Once out of the oven, allow cookies to cool on the baking sheet for five minutes before transferring them to a wire rack. Brush the cookies with the reserved 2 tablespoons of melted butter and sprinkle them with the cinnamon sugar or toss them in the cinnamon sugar.
• Allow cookies to cool completely on a rack before filling them with either 1 1/2 tablespoons of Bourbon Caramel Buttercream or Brown Sugar Cream Cheese Icing and a teaspoon of Bourbon Caramel (if using). 

FOR THE BOURBON CARAMEL BUTTERCREAM (if using)

• In the bowl of an electric mixer fitted with the whisk attachment, beat the butter and salt on medium for 2-3 minutes until light and fluffy.
• Add the Bourbon Caramel and mix until the caramel is incorporated. Scrape down the sides of the bowl now and a few times while adding the powdered sugar.
• Turn mixer to low and add gradually add 1 cup of the powdered sugar until combined and smooth. Add the remaining powdered sugar as needed until it reaches the consistency you like. If frosting is too thin, add more powdered sugar. If it’s too thin, add milk or heavy cream. 

FOR THE BROWN SUGAR CREAM CHEESE ICING (if using)

• In a large bowl or the bowl of a stand mixer fitted with the paddle attachment, mix the cream cheese and butter on medium speed for one minute until creamed and combined. Add the brown sugar and mix on medium for another minute. Mix in the vanilla then turn the mixer on low and gradually mix in the powdered sugar. The frosting should be somewhat thick. Pipe or spread the icing on one half of the whoopie pie. Top with another cookie. Refrigerate whoopie pies 30 minutes before serving.