Preheat your oven to 350°F (175°C).
In a large bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
In another bowl, combine the granulated sugar, brown sugar, and vegetable oil until well blended.
Add the eggs and vanilla extract to the sugar mixture, mixing well until fully combined.
Gradually mix the dry ingredient mixture into the wet ingredients until just combined, then fold in the grated carrots.
Scoop the batter onto a lined baking sheet, using about 2 tablespoons per pie, spacing them a couple of inches apart.
Bake for 12-15 minutes or until the edges are lightly golden and a toothpick inserted comes out clean.
Remove from the oven and allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
In a clean bowl, beat the cream cheese and softened butter together until smooth and creamy for the frosting.
Gradually add the powdered sugar and vanilla extract, mixing until fully incorporated and smooth.
Once the whoopie pies are cool, spread frosting on the flat side of one pie and sandwich with another pie.
Serve immediately or refrigerate for a firmer frosting, then enjoy!