Preheat oven to 325°
Prepare a 9.5" bundt pan with a baking spray or butter or shortening and flour pan thoroughly. Alternative pan size 13x9, 2-8" round pans, 2-8" loaf pans.
In a small bowl combine the cocoa and coffee.
In a medium bowl combine the flour, sugar, baking soda, and salt.
In another medium bowl whisk the eggs, sour cream, oil, and vanilla until smooth.
Pour the egg mixture into the flour mixture and stir until everything is combined, then pour in the coffee mixture and stir until smooth and creamy.
Place batter into a prepared bundt pan and bake for 50 minutes or until a. toothpick comes out clean. Adjust the timing if you use an alternative pan size, start testing at 25 minutes for round pans, and 30 minutes for 13x9 or loaf pans.
Frosting
In the bowl of a mixer beat butter until smooth on high add in sour cream and mix on medium, then on low add in the cocoa, powdered sugar, and vanilla, continue mixing and raising the speed until the frosting is whipped and fluffy.
Allow cake to cool for 10 minutes, then turn onto a wire rack to cool for about 20 minutes.
Then slather the frosting on top, it'll move down the sides and middle.
If your cake is too warm the frosting will melt. 30 minutes of pooling should be ok.