Preheat oven to 325ºF. Line two cookie trays with parchment paper. In a medium bowl, mix together the oil, pumpkin, applesauce, salt, syrup, and vanilla. In another medium bowl, whisk together flour, flax seed, baking soda, and xanthan gum. Stir together the wet and dry ingredients until just combined. Let batter rest for a couple of minutes before making cookies.

Using a small portion scoop or a teaspoon, scoop dough onto prepared trays, spacing 2 inches apart. Gently press with spatula to flatten slightly. Bake for 12 to 15 minutes and transfer to a wire cooling rack; cookies need to be completely cooled before assembling so that the filling doesn’t melt.

To make cream cheese frosting, use an electric or stand mixer to beat cream cheese. Gradually add vegan butter, and continue beating until smooth and well blended. Sift in powdered sugar and vanilla. Continue beating until smooth. Frosting should be firm and stiff. If it's too thin, add a little more powdered sugar by the tablespoon until desired consistency is reached.

To assemble whoopie pies, place dollop of frosting on one cookie then top with another cookie. Set aside and repeat until all the cookies have been used. Serve immediately, or store, covered, in the refrigerator. These are best served at room temperature.