Preheat your oven to 325 F. Use either 3 8-inch pans. Spray the bottom of the pans, line with parchment paper, and then spray again. Set aside.
In a stand sized mixer fitted with the paddle attachment, combine the flour, sugar, cocoa powder, baking soda, baking powder, and salt. Mix on low until evenly combined.
In a small bowl, whisk the eggs, buttermilk, hot water, vanilla extract, and vegetable oil until evenly combined.
With the mixer on the lowest speed, pour the liquid ingredients into the dry ingredients and mix just until combined. There should be no flour streaks. With a rubber spatula, scrape the bottom of the bowl to make sure the batter is evenly combined.
Divide the batter evenly between the pans (about 15 ounces in each 8 inch pan) and bake for 30-33 minutes. After they are done baking, let them cool for 15 minutes in the cake pans and then transfer them to a cooling rack and let them finishing cooling there.
After the cakes have come to room temperature, level the tops of the cakes, if needed, and then wrap them in plastic wrap and freeze them in preparation for frosting the cake.
For the peanut butter buttercream
In the bowl of electric mixer fitted with the paddle attachment, combine the butter and peanut butter. Beat on medium-high speed until smooth, about 2 minutes.
With the mixer on the lowest speed, add the powdered sugar, vanilla, salt, and cream to the bowl. Once mixed, beat on high for 3 minutes, scrape down the bowl and beat for 1 more minute. It should look light and fluffy.
Use a wooden spoon to mix frosting one last time to get rid of air bubbles.
For the ganache
In a microwave proof bowl, heat the cream until it becomes bubbly, while the cream is heating, add the chocolate wafers to a small bowl.
Once the cream is hot, add it to the chocolate, cover with plastic wrap and let it sit for 5 minutes, Stir to combine.
Assembly
Level each of the cake layers. Spread a small amount of frosting on a cake board to help hold the cake in place.
Place the first cake layer, bottom-side down, in the center of the cake board. Using an offset spatula, spread about ½ to ⅔ cup frosting evenly across the cake layer. Drizzle some of the chocolate ganache right on top.
Place the second cake layer on top of the peanut butter frosting layer and repeat step 2.
Place the final cake layer, bottom-side up, on top of the second peanut butter frosting layer and give the cake an even crumb coat, making sure to fill in uneven areas of the cake to create an even foundation for your main frosting. Freeze the cake for 10 minutes to set the crumb coat.
Frost the rest of cake and then add the drip ganache. Serve cold or room temperature.