Preheat the oven to 350°F. Line two large baking sheets with parchment paper or silicone baking mats. Set aside.
Whisk together the flour, cocoa powder, baking soda, and salt and set aside.
In a large bowl using a hand-held or stand mixer fitted with a paddle attachment, beat the butter for 1 minute on medium-high speed until completely smooth and creamy. Add the brown sugar and beat on medium high speed until fluffy and combined. Beat in the egg high speed, scraping down the sides and bottom of the bowl as needed. Once egg is full combined, beat in the vanilla extract and buttermilk.
On low speed, gradually mix the dry ingredients into the wet ingredients until just combined. Add food coloring until you reach your desired red hue. Scoop 1½ tablespoon mounds of batter onto prepared baking sheets.
Bake the cookies for 10-12 minutes or until centers appear set. Allow to cool completely before sandwiching.
In a large bowl using a hand-held or stand mixer fitted with a paddle or whisk attachment, beat the cream cheese for 1 minute on high speed until completely smooth and creamy. Beat in the butters until combined. Add the powdered sugar and vanilla and beat on medium-high speed until combined and creamy.
Match the cookies up based on their size and shape. Spread cream cheese filling onto the flat side of one cookie and sandwich with the other. I use the same scoop I used for the cookies for a perfect cookie to filling ratio.