Chocolate Cake: Preheat your oven to 350 degrees F (180 degrees C) and place the oven rack in the center of the oven. Butter, or spray with a non stick vegetable spray, two - 8 x 2 inch (20 x 5 cm) round cake pans. Then line the bottoms of the pans with parchment paper. 

In the bowl of your electric stand mixer, fitted with the paddle attachment, (or with a hand mixer) beat the sugar, flour, cocoa powder, baking soda, baking powder, and salt until combined.

In another large bowl, whisk together the eggs, buttermilk, oil, and vanilla extract. On low speed, add 1/3 of the wet ingredients to the dry ingredients and beat until the mixture is a thick smooth paste. Add another 1/3 of the wet ingredients and mix, on low speed, until the batter is nice and smooth. At this point, scape down the sides and bottom of your bowl. Finally, add the rest of the wet ingredients and beat until incorporated and you have a smooth batter.

Evenly divide the batter between the two pans (about 670 grams in each pan) and bake for about 35 - 40 minutes or until a toothpick inserted into the center of the cake just comes out clean and the cakes are just starting to pull away from the sides of the pans.  

Remove from oven and let cool on a wire rack for about 15-20 minutes. Then remove the cakes from their pans and cool completely on a greased wire rack before frosting. (The unfrosted cakes can be frozen for one month. Defrost in the refrigerator overnight.)

Chocolate Ganache: Place the chopped chocolate in a  heatproof bowl. Set aside. Heat the cream in a small saucepan over medium heat. Bring just to a boil. (Can also heat the cream in the microwave, but watch carefully.) Immediately pour the boiling cream over the chocolate and allow to stand, without stirring, for a few minutes. Then, using a heatproof spatula, and starting in the center, stir the chocolate mixture in circles until the chocolate has melted and the ganache is nice and smooth. Immediately cover with plastic wrap, and let sit, at room temperature, until the ganache is of spreading consistency. This can take several hours (I let it sit overnight).

Peanut Butter Frosting: In the bowl of your electric stand mixer, fitted with the paddle attachment (or with a hand mixer), beat the cream cheese and butter, on medium speed, until smooth. Add the remaining ingredients and beat, on medium speed, until light and fluffy. (The frosting can be refrigerated for five days or frozen for about two months. The frosting will have to be brought to room temperature and rewhipped.)

Assemble: Cut the two cake layers in half horizontally (so you will have four layers of cake). Place one cake layer (top of the cake facing up) onto a 9 inch (23 cm) cake circle. Spread with about 1/3 (1/2 cup (160 grams)) of the peanut butter frosting. Place the next cake layer, cut side down, onto the peanut butter frosting and spread with about 1/2 cup (150 grams) of ganache. Top with another layer of cake and spread with another 1/3 (1/2 cup (160 grams)) of the peanut butter frosting. Finally, top with the fourth layer of cake, bottom of the cake facing up, and cover the entire cake with a very thin layer of Ganache (using a scant 1/2 cup (150 grams)) (this is called a crumb coat). Refrigerate the cake for about 30 minutes or until the Ganache has set. Once the Ganache has set, spread the remaining Peanut Butter Frosting on the top of the cake, using a spatula to create a swirl pattern. Place the cake in the refrigerator and chill until the peanut butter frosting is set (about 15 - 30 minutes). Then spread a very thin layer of Ganache on the sides of the cake and, if desired, press chocolate shavings or curls into the Ganache.

The finished cake can be covered and stored in the refrigerator for about three days or frozen (well wrapped) for about one month. (If freezing, defrost in the refrigerator overnight.) Bring the cake to room temperature before serving.

Serves about 12 - 14 people.