In a large bowl, whisk together flour, baking powder, baking soda, pumpkin pie spice, cinnamon, and salt.
In a separate bowl, use a hand mixer to beat together softened butter and Truvia® Sweet Complete™ on medium speed for about 2 minutes.
Add eggs one at a time, beating well to integrate each.
Add pumpkin puree and vanilla extract, beating until smooth.
Pour half of the flour mixture into the wet mixture, beating until integrated, then continue with the other half of flour mixture.
Drop heaping spoonfuls of dough (or use a cookie scoop to portion) onto a baking sheet lined with parchment and sprayed.
Bake 13-16 minutes, until springy to the touch.
Cool on baking sheets for 5 minutes and then transfer to wire baking racks to cool completely before frosting.
To make filling & assemble whoopie pies:
To a large bowl, add softened cream cheese, butter, vanilla extract, cinnamon, and nutmeg. Beat together with a hand mixer on medium speed, until fluffy.
Gradually beat in Truvia® Confectioners, adding ½ cup at a time, until light and fluffy.
Spread a heaping teaspoon of frosting onto the flat side of one cookie, and top with a second cookie to make a sandwich. Repeat to assemble as many whoopie pies as desired.
Cover or store assembled whoopie pies in an airtight container in the fridge for up to a week. Store unfrosted pumpkin spice cookies in an airtight container at room temperature. (For best results, assemble whoopie pies at the time of eating with freshly whipped frosting!)
Yields 44 pumpkin spice cookies, or 22 assembled whoopie pies.