In a medium bowl, whisk together flour, ginger, cinnamon, baking powder, baking soda, and salt. Set aside.
With a whisk, beat together pumpkin puree, brown sugar, oil, eggs, and molasses until mixed and fluffy.
Gradually add flour mixture and stir to incorporate.
(Cover and refrigerate batter until chilled, about 30 minutes.)
Preheat the oven to 180°C/350°F fan.
Transfer batter to a pastry bag fitted with a plain tip. Pipe circles onto parchment-lined baking sheets, spacing whoopies apart.
Bake for 3 minutes. Leave to cool completely on tray.
Make the filling of your choice
Turn half the whoopies over so they're bottom-side up. Using a pastry bag or butter knife, add a dollop of Maple-Spice Filling onto each whoopie bottom. Top with remaining whoopies.
To decorate: Melt the marshmallow and then make it into a web with your fingers. Place it on top of the whoopie pie. OR Place the icing in a piping bag and drizzle a ghost shape onto the whoopie pie, use the black food colouring with a toothpick to make eyes. OR Place the melted orange candy melts in a piping bag and draw pumpkin lines on the whoopie pie. Place a mint leaf on top for the stem.