For the Cake

1. Preheat the oven to 350°F. Prepare two 8-inch round baking pans, line the bottom with parchment paper, and grease and flour the sides of the pan.
2. Using the large cheese grater, grate the peeled sweet potato. Alternatively, you could use a food processor for smaller pieces. Set aside. 
3. In a large mixing bowl, combine the eggs, oil, sour cream, and vanilla extract. Beat all the ingredients together until well combined. Add the sugar and beat until incorporated, then mix in the sweet potatoes. 
4. Sift the remaining dry ingredients in a large bowl and whisk to combine. Add the dry and wet ingredients and begin mixing while slowly streaming in the coffee. Beat at a low speed until well combined.
5. Divide the batter evenly between the two pans, about 2 ¾ cups of batter each. Bake at 350°F for 30-35 minutes.  Test the cake for doneness by inserting a toothpick into the center of the cake. If the toothpick comes out clean, the cake is done. Remove from the oven and allow to cool completely.

For the Frosting

1. Cut the butter into 1-inch blocks. Beat the butter for 3-4 minutes until it’s softened and whipped.
2. Then add the cream cheese and cream together for 2-3 minutes until they are fluffy and free of lumps, and scrape down the bowl occasionally.
3. Next, Add the cocoa powder and vanilla extract and beat until well combined,
4. To finish, add the confectionary sugar 2 cups at a time and beat for 60-90 seconds until completely smooth before adding more. Reserve the heavy cream only if needed to thin out the frosting.
5. Level the cake layers if needed. Place a dollop of frosting on your cake board and place the bottom layer of cake on top of that. Place half of the frosting in a large piping bag, then cut off the end of the piping bag.  Pipe the first layer of frosting, pipe in circles working outside edge to the middle. Spread evenly with an offset spatula. Place the second layer inverted of the cake.
6. Use the piping bag to fill in any gaps between the layers and to create a crumb coat. Using an offset spatula or icing smoother, wipe away the excess frosting, leaving you just enough to coat the outside of the cake. With the remaining frosting, pipe the frosting along the outside edge of the cake using a large open round tip then use an offset spatula to smooth the edges. Use any remaining frosting to decorate with.