Turn the Crock Pot on High, and place the Stick of Butter in the bottom of the Crock Pot, until it starts to melt. Add the Eggs and Sugar, and mix together, until the mixture is creamy.
Add the Oil, and Milk, and stir well. Add the Flour, salt, Cocoa, Baking Soda and blend. Add the Vanilla, and the Coca Cola, and mix until blended.
Place the lid on the Crock pot, and leave the Heat on HIGH for 30 minutes, then turn the Heat setting to MEDIUM, and cook for another 30 minutes. Turn the Heat off, and let the cake cool for an hour to two hours.
FROSTING:
In the mixing bowl of a stand mixer, place the Butter, Cocoa, Milk, and Vanilla, and blend on low until mixed. Add the Powdered Sugar a little at a time until the Frosting starts to thicken, or all the Sugar is added.
If Frosting is too thick, add a few more drops of Milk, if its a little thin, add a little more Sugar, until you have a nice thick, but spread-able Frosting.
Frosting the Cake right in the Crock Pot, using all the Frosting, and cut into 3 X 3 inch pieces to serve. Enjoy!