Preheat oven to 350°F. Butter two 8" cake pans and dust with cocoa. Combine all dry ingredients in the bowl of a mixer and mix until combined. In a small bowl, combine buttermilk, oil, eggs, and vanilla. Pour buttermilk mixture into dry ingredients and beat just until smooth. Mix coffee and cocoa together,add to mix just until combined. Divide batter, evenly between the two pans. Bake for 35 to 40 minutes until a toothpick stuck in the center of each cake comes out clean. Remove from oven and allow to cool in the pans for 10-15 minutes before turning out onto a wire rack to cool completely. Frost cake.
Frosting:Combine melted chocolate,butter and vanilla,add sugar to combine into a fluffy frosting. If too stiff,add addition butter.
Combine all ingredients in the bowl of a food processor. Pulse until well-combined. If you don't like the consistency (but you will!), you can add more powdered sugar or half-and-half and continue to pulse until the frosting is just the way you like it.