In a medium pot, bring the apple cider to a rolling boil. Boil-off the water for at least 10 minutes then check the amount of syrup. Keep boiling if needed to reduce the apple cider to 1/3 cup of syrup.

Mix together the dry ingredients - flour, cinnamon, baking powder, salt, baking soda, and nutmeg. Whisk to combine. Set aside.

When the apple cider has been reduced to 1/3 cup, remove it from the heat and transfer to a large bowl. Add in the butter. Mix until the butter is melted.

Add in the brown sugar and mix until the sugar has been completely incorporated.

Mix in the applesauce, buttermilk, and eggs.

Stir in the dry ingredients and mix until a sticky dough forms. Cover and chill for 1 hour in the fridge.

Combine sugar and apple pie spice together and set aside.

Add 2 quarts of oil to a large pot, like a Dutch oven making sure that the oil is at least 1 1/2 inch deep. Use a candy thermometer and heat the oil to 350F.

While the oil is heating, roll out the doughnuts. Flour your work surface and transfer the dough. It will be sticky and lumpy. Dust the top of the dough with more flour. Roll the dough out to 1/2 inch thickness making sure that it's not sticking to the work surface.

Cut our doughnuts with a doughnut cutter or use a 3-inch round cookie/biscuit cutter. Transfer the cut doughnuts to a cookie sheet then reroll the leftover dough and repeat until all the dough is used up. This should make 10 - 12 doughnuts plus holes.

Very carefully place 1 doughnut at a time into the oil. Do not overcrowd the pot. Work with 2 - 4 doughnuts at a time. Use tongs to flip the doughnuts over after 60 to 90 seconds of frying. When the doughnuts are done cooking, immediately transfer them to the spiced sugar to coat them. Cool on a wire rack.

Make the Whoopie Pie Filling

Beat the butter and marshmallow creme until light and fluffy.

Gradually add powdered sugar and apple pie spice.

Beat until smooth and creamy.

Cut the doughnut in half and spread the filling. Add decorative sprinkles if you want.

Store in an airtight container in the refrigerator until ready to serve.