Make the cake: Prepare three 8-inch round cake pans by spraying them with baking spray, then lining them with parchment paper circles. Spray the parchment paper circles.
Soak the Bake-Even strips (if using) in cold water for 5 minutes. Press out the excess water (do not wring), and wrap them snugly around the cake pans.
Preheat oven to 350°F.
In a small bowl, whisk together the buttermilk powder and hot water. You can skip this step if you're using warmed buttermilk (see Recipe Notes).
In the bowl of a stand mixer fitted with a paddle attachment (or using a hand mixer and a large bowl), stir together the flour, sugar, dark chocolate cocoa powder, baking soda, baking powder, and salt.
Add the eggs, buttermilk, vegetable oil and vanilla to the dry ingredients and mix well.
Slowly add the port wine. Mix gently, being careful not to overmix the batter.
Divide the batter evenly between the cakes pans, and tap out the pans on the counter to release any trapped air bubbles. Bake for 30 to 33 minutes, or until a cake tester comes out with a few crumbs. The cake is fudgy, so be careful not to overbake the cakes. Every oven heats differently, so start checking your cakes at the 25 minute mark.
Remove the cakes from the oven and allow to cool for about 10 minutes, then remove to cooling racks to cool completely. If you're not using Bake-Even strips, level the cakes before stacking.
Make the ganache: In a small saucepan over medium-low heat, add the heavy cream and port wine, stir together, and heat until steaming and bubbles begin to form.
Remove from heat, add the chopped chocolate, and cover for two minutes.
Open the lid and whisk the mixture until it's totally smooth. Set aside for about 30 minutes to cool. You want the ganache to be thicker and easily spreadable, but not too thin.
Assemble the cake: Using the cake lifters, place one layer on the cake stand. Be careful because the layers can be delicate. Pour some of the ganache onto the center of the cake and use a small offset spatula to gently push the ganache off of the side so that it drizzles down the sides of the cake.
Stack another layer on top and frost with ganache. Repeat with the third layer. If desired, frost the sides of the cake with ganache.
Decorate the cake as desired. You can whip some of the ganache and pipe roses on top, or use sprinkles and cocoa nibs to decorate. Any leftover ganache can be scooped into balls and made into truffles...use those to decorate the cake.
Chill the cake to firm up the ganache before slicing. Serve and enjoy!
Cake pan alternatives: you can adjust this recipe to make the size cake you'd like as follows:
For a single layer mini cake: divide the ingredients by 4 (use a whole egg). Bake in a 6-inch round cake pan for 25 to 28 minutes.
For a two layer mini cake: divide the ingredients by 2. Bake in two 6-inch round cake pans for 25 to 28 minutes.
I use dried buttermilk powder mixed with hot water, but you can substitute regular buttermilk (omit the hot water)Using hot liquid helps the cocoa powder "bloom," i.e. get fully hydrated as it mixes into the batter. If you're using regular buttermilk, heat it gently until it's steaming with small bubbles. Don't let it boil.Using the Bake-Even strips helps keep the cakes level as they bake. If you prefer not to use them, level the cakes after they've cooled before stacking.