Preheat the oven to 350 degrees F. Line baking sheets with parchment paper or silpat mats.
MAKE THE PIES:
In a small bowl, combine the cocoa powder, food coloring and water. Mix to combine; set aside.
In a large bowl, whisk together the sugar, oil and eggs. Add in the buttermilk, vanilla extract, salt and food color mixture. Whisk to combine. Stir in the flour, just until combined.
In a small bowl, dissolve the baking soda in the vinegar; pour into the batter and stir to combine.
Spoon the batter carefully onto prepared cookie sheets, making sure that they are as round as possible (you can use a cookie scoop for this too). They’ll spread a little bit so just spoon about a tablespoon for each.
Bake for about 6 to 7 minutes, until they’re set and no longer sticky or soft. Let cool before filling.
MAKE THE FILLING:
In a medium bowl, use an electric mixer to beat the cream cheese, marshmallow crème and butter together until smooth. Add in the powdered sugar and vanilla. Spread a tablespoon or so onto the bottom side of a pie, then top with the bottom side of another pie. Store in the refrigerator, keeping the pies in a single layer. Cover with plastic wrap to keep fresh.
Notes
*I prefer to use gel or paste coloring, which doesn’t impart the “food color” flavoring to your baked good. If you use gel or paste, add about a teaspoon of it to the cocoa, then add 1/4 cup of water (instead of 2 tablespoons) and mix together. Re-evaluate the color of the batter after step 4- if you’d like it to be a deeper hue of red, add a few more drops of red.
*If you have one, use a one tablespoon scoop (like a little ice cream scoop) to place the batter on the cookie sheets.