1. Prepare Oven and Pans:

• Preheat oven to 350°F (180°C).
• Spray the bottom of three 8-inch round cake pans with cooking spray. Line the bottoms with parchment rounds. Set aside.

2. Mix Dry Ingredients:

• In a large mixing bowl (preferably the bowl of your stand mixer), sift together the flour, sugar, black cocoa powder, baking soda, baking powder, and salt. Whisk briefly to combine.

3. Mix Wet Ingredients:

• In a separate medium bowl or large measuring cup, combine the room temperature buttermilk, hot coffee, vegetable oil, and vanilla extract.
• Whisk in the room temperature eggs until combined.

4. Combine Batter:

• Add the liquid mixture to the dry ingredients in the mixer bowl.
• Whisk (or mix on low speed with paddle attachment) until smooth, about 1 minute. Scrape down the bowl as needed. Batter will be thin.

5. Bake the Cake Layers:

• Divide the batter equally among the three prepared cake pans (approx. 630g per pan if weighing).
• Bake for about 23 minutes (this seems short for 8-inch pans, might need closer to 28-33 min – start checking early), or until a wooden pick inserted into the center comes out with only a few moist crumbs attached. Try not to over-bake.
• Let cakes cool in the pans on a wire rack for 10 minutes.
• Carefully invert the cakes onto the wire rack, remove parchment paper, and let cool completely.
• Optional but Recommended: Once cool, wrap layers tightly in plastic wrap and chill for about 30 minutes before frosting (makes assembly easier).

6. Make the Dark Fudge Frosting:

• In the bowl of a stand mixer fitted with the paddle attachment, beat the softened butter on medium speed until pale and fluffy, about 6 minutes.
• Sift together the confectioners’ sugar and cocoa powder(s) into a separate bowl.
• Reduce mixer speed to low. Gradually add the sifted sugar/cocoa mixture to the butter.
• Add the hot water, sour cream, vanilla extract, and salt. Beat on low until just incorporated, about 1 minute. Scrape down the bowl.
• Increase the speed to medium and beat for 2 more minutes until combined.
• Add the melted and slightly cooled dark chocolate. Beat on medium speed until smooth and fully incorporated, about 1 minute.
• Optional final whip: Increase speed to medium-high/high and beat for another 2-5 minutes if a slightly lighter/fluffier texture is desired (recipe implies beating longer after adding chocolate).

7. Assemble the Cake:

• If necessary, level the tops of the chilled cake layers. Place the first layer, top-up (or leveled side up), on your cake board or serving plate.
• Spread about 1 cup of the frosting evenly across the layer.
• Place the second cake layer on top and repeat with another layer of frosting (about 1 cup).
• Place the final cake layer on top, upside down for a flat top surface.
• Cover the cake loosely with plastic wrap and gently wiggle/press the layers to ensure they are level and stable, if necessary. Refrigerate the cake until firm, about 20 minutes.

8. Crumb Coat and Final Frost:

• Remove the cake from the refrigerator. Place it on a turntable if using.
• Apply a thin layer of frosting over the entire outside of the cake (top and sides) to seal in the crumbs. Chill again until the frosting begins to firm up, about 15 minutes.
• Remove the cake from the refrigerator. Apply a thick, even layer of the remaining frosting over the top and sides of the cake.

9. Decorate with Comb and Piping:

• Hold a pastry comb vertically against the side of the cake with gentle, even pressure. Rotate the turntable smoothly one full rotation to create textured lines. (If unsatisfied, smooth frosting and repeat).
• Fill a large pastry bag fitted with a large plain round tip (like Ateco #809) with the remaining frosting.
• Pipe decorative “poofs” around the top perimeter of the cake: Hold the bag straight up, tip close to the surface, squeeze gently for about 2 seconds, stop squeezing, then lift straight up. Repeat around the edge.

10. Add Sprinkles and Serve:

• Gently toss or press your favorite sprinkles onto the bottom 1-2 inches of the cake sides.
• The cake is best enjoyed at room temperature. Let it sit out for 30-60 minutes before serving if refrigerated.
• Store leftover cake in an airtight container at room temperature for up to 2 days or refrigerated for up to 3-4 days.