Heat oven to 350F.
Whisk flour, cinnamon, nutmeg, allspice, baking powder, baking soda & salt in medium bowl.
Use a stand mixer with a paddle attachment to cream brown sugar and butter for 2 minutesAdd oil, applesauce, egg and vanilla until smooth.
Slowly add dry ingredients until combined.
Use a cookie scoop to make even sized balls of batter 2 inches apart on a parchment paper lined baking sheet. Bake for 10 to 12 minutes.
Remove from oven and cool completely.
Place all of the filling ingredients in a large bowl or your stand mixer and beat until fluffy.
Spread filling on the flat side of half the cookies. Sandwich with remaining cookies and store in the fridge - serve at room temperature.