Preheat & Prepare: Preheat your oven to 350°F (175°C) and grease your 8-inch cake pans.
Mix Cake Ingredients: In a mixing bowl, combine the cake mix, cocoa powder, buttermilk, corn oil, eggs, and vanilla. Mix on low for 1 minute, then scrape the sides and mix on medium for 2 minutes until smooth.
Bake: Pour the batter into the prepared pans and bake for 30-40 minutes, or until a toothpick inserted comes out clean. Let the cakes cool in the pan for 5 minutes before transferring to a wire rack to cool completely.
Make Ganache: In a double boiler, melt the chocolate chips and whipping cream together, stirring until smooth. For a thinner ganache, add an extra 1/4 cup of cream.
Layer the Cake: Once the cakes have cooled, place the bottom layer on your serving plate. Spread a generous amount of ganache on top, then add a thin layer of cherry pie filling.
Top Layer & Final Touch: Add the top layer of cake, then pour the remaining ganache on top. Let it drip down the sides for a beautiful effect. Add a circle of cherry pie filling in the center of the top layer.
Serve & Enjoy: Slice, serve, and enjoy this decadent birthday treat!