1) To make the cookies: Preheat the oven to 375°F. Grease two baking sheets or line with parchment paper.
2) Beat together the butter, oil, sugar, molasses, cake enhancer, baking powder, baking soda, salt, and spices.
3) Scrape the bottom and sides of the bowl, then beat in the eggs one at a time, until fluffy.
4) Stir in the pumpkin.
5) Add the flour in two additions, mixing well after each addition.
6) Use a muffin scoop to deposit the thick batter onto the prepared baking sheets, leaving about 2" around each mound.
7) Bake until the cookies feel firm; a slight indentation will remain when you gently press them in the middle, about 16 to 18 minutes.
8) Remove from the oven, cool on the baking sheets for 5 minutes, then move to a rack to cool completely.
9) To make the filling: Beat the cream cheese and butter until smooth and fluffy.
10) Beat in the sugar in two additions.
11) Add the vanilla and xanthan gum. Beat for 2 to 3 minutes, until very fluffy.
12) Stir in the crystallized ginger.
13) To assemble: Sandwich two cookies around 2 tablespoons of filling. For best storage, wrap each pie in plastic wrap.
Yield: 1 dozen 4" whoopie pies.