Preheat the Oven and Prepare Baking Sheets:
Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
Mix the Dry Ingredients:
In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
Prepare the Wet Ingredients:
In a separate large bowl, beat the vegetable oil and granulated sugar together using an electric mixer until the mixture is smooth and creamy.
Add the eggs, one at a time, beating well after each addition.
Stir in the vanilla extract and red food coloring. The red food coloring will give the pies that signature vibrant color.
Mix in the white vinegar, which helps activate the baking soda for a light, fluffy texture.
Combine Wet and Dry Ingredients:
Alternately add the dry ingredients and buttermilk to the wet ingredients, starting and ending with the dry ingredients. Mix until just combined, being careful not to overmix the batter.
Scoop the Batter:
Using a spoon or a cookie scoop, drop rounded tablespoonfuls of batter onto the prepared baking sheets. Space each scoop about 2 inches apart to allow for spreading.
Bake the Pies:
Bake in the preheated oven for 10-12 minutes, or until a toothpick inserted into the center of the pies comes out clean. The pies should be slightly firm on the outside but soft in the middle.
Remove from the oven and let them cool on the baking sheets for a few minutes before transferring them to a cooling rack to cool completely.
Make the Cream Cheese Filling:
While the pies cool, make the cream cheese filling. In a large bowl, beat the softened cream cheese and butter together until light and fluffy.
Gradually add the powdered sugar, one cup at a time, mixing until smooth and creamy.
Stir in the vanilla extract and a pinch of salt for flavor balance.
Assemble the Whoopie Pies:
Once the pies have cooled completely, spread or pipe a generous amount of cream cheese filling onto the flat side of one pie.
Top with another pie, pressing gently to sandwich the filling in the middle. Repeat with the remaining pies.
Serve and Enjoy:
Serve immediately, or store the whoopie pies in an airtight container in the fridge for up to 3 days.