Preheat the oven to 375 F. Line 2 baking sheets with parchment paper or silicone and set aside.

Dump the pumpkin, eggs, brown sugar, oil and molasses into a large bowl. Whisk together just until smooth. Switch to a silicone spatula, and beat in the salt, spices, baking powder and baking soda. Fold in the flour gently and then beat for 1 minute until smoothly combined.

I prefer a smaller whoopie pie, so I used a mid-sized cookie scoop to scoop out the batter onto the prepared sheets, leaving 2 inches between "blobs" for spreading. You could go as high as a 1/4 cup scoop.

Bake the cookies for 8-12 minutes (depending on what size scoop you used), or until they feel firm to the touch and have that slightly dried out look (instead of looking wet and batter-like). Let the cookies cool for 5 minutes on the sheet before transferring to a cooling rack to cool completely.

While the cookies are baking and cooling, begin working on the filling.

Pour the water over the gelatine in a small microwaveable bowl. Set it aside to soften.

Beat the butter and cream cheese until fluffy, using a hand held or stand mixer. Heat the softened gelatine very gently (about 30% power, short increments) in the microwave to dissolve the gelatine--stir it occasionally. Set aside.

Add half of the confectioners' sugar to the fluffy butter mixture and beat it in. Beat in the dissolved gelatine. Add the remaining confectioners' sugar and beat it smooth.

When the cookies have cooled, assemble the whoopie pie by spreading a tablespoon or 2 of filling onto the bottom of one cookie and covering it with another cookie, bottom side down towards the filling.