In a saucepan, mix coke, oil, butter and cocoa and bring to aboil. In another bowl, combine the sugar, flour, and salt. Pour the boiling Coke mixture over the flour mixture and beat well. Add the eggs, buttermilk, soda and vanilla and beat well. Pour mixture into a greased andfloured 13 x 9 inch baking pan and bake at 350 degrees for 20 to 25 minutes or until toothpick inserted in center comes out clean. Let cool for 10 minutes before frosting. Cake needs to be warm for frosting.

Frosting: In a saucepan, combine the butter, cocoa, and milk. Heat until the butter melts. Beat in the remaining ingredients and spread on the cake while it is still warm.