In a large mixing bowl fitted with the paddle attachment, mix together butter and sugars on medium speed for about 2 minutes, or until all combined.
Add egg, vanilla and red food coloring and mix together until fully incorporated.
Slowly mix in baking soda, salt, cocoa powder and flour until just combined. Scoop dough into 1½ tablespoon size cookie balls and chill for a few hours. You should have about 20 cookies.
Preheat oven to 350 F. Line 2 baking sheets with parchment paper.
Roll chilled cookie dough balls in sugar and bake 10-12 cookies per sheet for 8-9 minutes, or until edges are cooked. Allow cookies to cool.
Buttercream
In a large mixing bowl, cream together butter, cream cheese and vanilla until smooth. Add powdered sugar and beat until light and fluffy. You may end up needing to add more powdered sugar or a little milk to get your desired consistency.
Using the same 1½ tablespoon cookie scoop, scoop buttercream and place on the bottom of 10 cookies. Take the extra 10 cookies and press lightly on top of the frosting to create a sandwich/oreo.
Notes
I love these cookies chilled and stored in the fridge, but do whatever you prefer.You may need to add more or less powdered sugar and milk to get the desired consistency for the buttercream. You want it to be thick so it doesn't ooze out when you bite into it.I have given both cups and grams as measurements. Grams will be more precise, especially when measuring flour. If you don’t have a kitchen scale, no problem! Just lightly spoon flour into your measuring cup to insure its not packed in there. Light and fluffy is the key.