Make the Red Velvet Cakes

1. Preheat the Oven: Preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper.
2. Prepare Dry Ingredients: In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
3. Cream the Butter and Sugar: In a large bowl, cream together the butter and sugar using an electric mixer until light and fluffy, about 2-3 minutes.
4. Add the Eggs and Vanilla: Beat in the eggs, one at a time, followed by the vanilla extract.
5. Incorporate the Red Food Coloring: Add the red food coloring and mix until fully combined.
6. Alternate Dry Ingredients and Buttermilk: Gradually add the dry ingredients in three additions, alternating with the buttermilk, starting and ending with the flour mixture. Mix until just combined.
7. Add Vinegar: Stir in the vinegar to activate the baking soda.
8. Scoop the Batter: Using a cookie scoop or spoon, drop tablespoon-sized portions of the batter onto the prepared baking sheets, spacing them about 2 inches apart.
9. Bake: Bake for 8-10 minutes, or until the cakes spring back when lightly pressed in the center.
10. Cool: Let the cakes cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.

Prepare the Cream Cheese Filling

1. Beat the Cream Cheese and Butter: In a large bowl, beat the softened cream cheese and butter together until smooth and creamy.
2. Add Powdered Sugar: Gradually add the powdered sugar, beating until smooth and fluffy.
3. Flavor with Vanilla and Salt: Add the vanilla extract and a pinch of salt, and beat until well incorporated. The filling should be thick but spreadable.

Assemble the Whoopie Pies

1. Pair the Cakes: Once the red velvet cakes have cooled, pair them up by size. Choose two similarly sized cakes for each whoopie pie.
2. Fill the Pies: Spread a generous amount of cream cheese filling on the bottom of one cake in each pair, then gently press the other cake on top to form a sandwich.
3. Serve: Once assembled, the whoopie pies are ready to enjoy!