In a medium bowl, combine flour, pumpkin pie spice, cinnamon, baking soda and salt. Whisk to combine. Set aside
In a large bowl, add egg, brown sugar, pumpkin and apple sauce. Mix on medium for 4 to 5 minutes until smooth and light brown in color.
Add flour to egg mixture and mix until combined. Do not over mix
Place 1 tablespoon in each well of a whoopie pie pan or pipe or drop a tablespoon on a parchment lined cookie sheet. Leave about 2 inches between each one.
Bake at 350 for 7 minutes. While they are cooking, prepare filling
Filling
In a bowl, sift confectioners sugar. Add in butter, syrup, marshmallow cream and cream cheese.
Beat until smooth and fluffy. About 4 minutes on med-high
Refrigerate while cookies are cooking and cooling. so it sets up a bit.
Assembly
Place a little less than a tablespoon on the flat side of one cookie, top with another cookie. Store in refrigerator.