FOR THE APPLE CIDER WHOOPIE PIES

• 2 cups apple cider reduced to 1/4 cup
• 1/2 cup unsalted butter, room temperature, divided (6 tablespoons for the dough and 2 tablespoons melted for brushing the baked cookies)
• 1 3/4 cups flour
• 1/2 teaspoon salt
• 1 teaspoon baking powder
• 1/4 teaspoon baking soda
• 1 1/2 teaspoons cinnamon
• 1/4 teaspoon ginger
• 1/2 teaspoon nutmeg
• 1/2 cup granulated sugar
• 1/4 cup plus 2 teaspoons brown sugar, light or dark, packed
• 1/4 cup apple butter or applesauce
• 2 eggs
• 1/4 teaspoon vanilla

FOR THE CINNAMON SUGAR COATING

• 3 tablespoons butter, melted
• 1/4 cup sugar
• 1/2 teaspoon cinnamon

FOR THE BOURBON CARAMEL BUTTERCREAM (if using)

• 1/2 cup unsalted butter, room temperature
• 1 1/4 – 1 1/2 cups powdered sugar, sifted (add gradually until desired consistency is reached)
• 2 tablespoons plus 2 teaspoons Bourbon Caramel Sauce, cooled to room temperature
• 1 pinch of salt

FOR THE BROWN SUGAR CREAM CHEESE ICING (if using)

• 4 1/2 ounces cream cheese, room temperature
• 3 tablespoons butter, room temperature
• 2 tablespoons brown sugar, light or dark
• 2 cups powdered sugar, sifted, plus more if needed
• 1/2 teaspoon vanilla extract
• 1 pinch salt