Preheat oven to 350°F (180°C). Liberally grease two 8" round cake pans with vegetable shortening, and/or spray with baking spray.
Combine flour, cocoa, sugar, baking powder, salt, and pudding mix in a large mixing bowl. Add in eggs and water, beating until smooth. Carefully add melted butter and vanilla to the mix, mixing on medium speed until smooth.
Divide batter among prepared cake pans. Bake until golden and knife inserted into center of batter comes out clean and cake springs back - about 45-60 minutes. Allow to cool 10-15 minutes before turning cakes out onto baking rack to cool fully. Ideally, allow to cool to room temperature, wrap tightly with plastic wrap. Allow cake to sit overnight.
Prepare Swiss meringue buttercream as described in recipe. Add blood orange essential oil and food coloring, if using. Continue to mix until well incorporated.
Place chocolate chips into a glass mixing bowl, and put aside. In a small saucepan, combine heavy whipping cream, essential oil, butter, and sugar. Heat to a boil, remove from heat. Pour hot cream mixture into bowl of chocolate chips. Let sit for 3-5 minutes. Starting in the middle of the bowl, slowly start stirring the chocolate and cream until all of the chocolate is melted and the cream has disappeared into it - it should be smooth.
Cover with plastic wrap, allow to cool to room temperature. Using a stand or hand mixer, whip for 2-3 minutes until fluffy.
To assemble cake:
Remove plastic wrap from cake layers. Carefully slice the domed top off each round, leveling the surface of the cake. Carefully cut each cake in half, horizontally, for 4 thin rounds of cake in all.
Place one round of cake on cake plate, spread with a thick layer of chocolate ganache. Top with a second round of cake, spread with a thick layer of blood orange buttercream. Top with a third round of cake. Spread with a final thick layer of chocolate ganache, and top with remaining layer of cake. Smooth out any frosting or ganache that may have bulged from between cake layers.
Chill for 30 minutes before frosting sides and top of cake with remaining buttercream. Serve at room temperature.
This cake gets VERY hard when chilled. Always serve cakes at room temperature! Cold cake is DRY cake.