Begin by making the whoopie pies. Preheat the oven to 350 degrees Fahrenheit. In a large bowl mix together all of the liquid ingredients until well blended. Add all of the dry ingredients and mix until thoroughly combined.
Scoop a tablespoon of the batter and place it onto a well-greased cookie sheet, making sure to place each tablespoon at least 3 inches away from the others, as the whoopie pies will spread out when they bake.
Place the pan in the oven and bake for 12 - 15 minutes, then remove the pan from the oven and allow the whoopie pies to cool for 20 minutes before attempting to remove them from the pan.
To make the filling, beat the egg white and vanilla extract together on high speed for 1 minute, or until the egg white mixture becomes slightly stiff and shiny.
Add the cream cheese and butter and continue to beat until the mixture becomes relatively smooth.
Add the powdered sugar and blend until thoroughly combined.
Then add the cocoa powder and blend until the coloring is consistent throughout the filling. Set it aside.
To assemble the whoopie pies, simply place a teaspoon to a tablespoon (depending on your filling preference) of the filling onto the bottom side of one of the whoopie pies.
Place another whoopie pie on top and voila, you made a complete whoopie pie! Continue to repeat this process until all of the whoopie pies have been assembled.