In a small bowl, combine powdered sugar, butter, unsweetened cocoa, liquid of your choice, and vanilla extract until mixed to a spreading consistency.
NOTE: Depending on how precise you are with your measuring, you may need to either add additional powdered sugar or liquid to get a good spreading consistency.
Spread on graham cracker squares.
Either eat open faced or press another square of a graham cracker on top.
Graham Cracker Chocolate Cookies Recipe: https://whatscookingamerica.net/cookie/chocgrahamcrackercookie.htm