Preheat your oven to 350°F. This is an important step to ensure that the cakes bake evenly. Line two cookie sheets with parchment paper or lightly spray them with cooking spray to prevent sticking.
In a large bowl, combine the spice cake mix, unsalted butter, pumpkin puree, eggs, and pumpkin pie spice. Use a mixer to mix slowly for about 30 seconds, just until combined. Then, increase the speed and beat for 1 to 2 minutes. The batter will be slightly wet and thick, which is perfect for these pies.
Using a tablespoon, drop dollops of batter onto the prepared cookie sheets. Make sure they are all roughly the same size for even baking. Leave enough space between each dollop, as they will spread while baking.
Place one pan in the oven at a time and bake for 10 to 11 minutes. You’ll want to keep an eye on them; they should look set and spring back when lightly touched.
Once baked, remove the pans from the oven and let the whoopie pies cool completely on the sheets. Patience is key here; they need to cool to hold their shape.
To prepare the frosting, in a medium bowl, combine the softened cream cheese and unsalted butter using an electric mixer until smooth. This should take just a few minutes. Once smooth, add the powdered sugar gradually while mixing on low speed.
After the sugar is fully incorporated, stir in vanilla extract and mix until the frosting is light and fluffy. If it seems too thick, you can add a splash of milk or cream for easier spreading.
Now, it’s time to assemble the whoopie pies! Take one cake, spread a generous dollop of frosting on the flat side, and top it with another cake, flat side down. Press gently to create a sandwich.
Store your Pumpkin Whoopie Pies in an airtight container in the refrigerator. They’re best enjoyed chilled, allowing the flavors to meld together.
