Chocolate Cake

1. Preheat oven to 350ºF. Prep two 9" cake pans by buttering the insides and lining the bottoms with parchment rounds. Dust the sides with cocoa and tap out any excess.
2. In the bowl of a stand mixer, whisk together the sugar, flour, cocoa powder, baking soda, and salt. Add buttermilk, butter, eggs, and vanilla and mix in on medium-low speed for about 3 minutes, stopping halfway to scrape down bowl (including bottom) and beater; batter should be very smooth when done. Add coffee and fold in with a rubber spatula until evenly combined. Note that the batter will be very liquidy.
3. Divide batter evenly between prepared pans and bake for 35-45 minutes, until a toothpick inserted into the center comes out clean or with just a few moist crumbs; cake edges should also be puling away from pan.
4. Cool cakes in pans for 15 minutes, and then transfer to a wire rack, peel off parchment, and cool completely. Once cool, wrap cakes tightly in plastic wrap, transfer to a large zip-top bag, and freeze for 30 minutes before decorating.

Cream Cheese Buttercream

1. In the bowl of a stand mixer fitted with the whip attachment, beat butter and cream cheese together on medium-high speed until smooth, wiping down bowl and beater as needed. With the mixer on low speed, gradually add the powdered sugar. Once completely incorporated, increase speed to medium-high again and beat until smooth and creamy, again wiping down bowl and beater as needed. Beat in vanilla extract and salt. Use a spatula to gradually mix in icing color (if desired).

Assembly

1. Place one cake layer on a cardboard cake round or plate set on a rotating cake stand (you may want to place strips of parchment under the edges of the cake to keep the bottom clean**). Spread a layer of frosting on top, and then place the second cake layer over the first.
2. Use an offset spatula to apply a thin layer of frosting to the cake over the top and sides to seal in the crumbs (this layer doesn’t need to be perfect). Transfer the cake to the refrigerator for 30 minutes to allow the crumb coat to set.
3. After chilling, apply a final, smooth layer of frosting all around the cake. Remove parchment strips, if you used them, and make sure bottom of decorating surface is completely clean before adding sprinkles.
4. Place a large tray below cake to catch any loose sprinkles. Cup sprinkles in the palm of your hand and carefully press against sides of cake, starting at the bottom and working your way up as high as you want, until entire perimeter of cake is covered as desired. (When doing this, you don't actually want your hands to touch the cake, but rather just get close enough to let the sprinkles fall from your palm onto the sides of the cake.) When done, brush off any fallen sprinkles as best as possible, and then carefully tilt cake to let remaining sprinkles fall onto tray below.
5. Transfer remaining frosting to a piping bag fitted with a large open star tip and pipe decoration around top of cake. Decorate with more sprinkles on top.
6. Cake is best served at room temperature, but any leftovers should be stored in an airtight container in the refrigerator and brought back to room temperature before serving.