Step 1 - Make the Butterbeer Cake. Preheat the oven to 350 degrees. Add cake mix, pudding mix, eggs, water and oil in a mixing bowl and mix until incorporated. Fold in vanilla extract and cream soda and immediately place into prepared 8X2 inch cake pans.
Step 2 - Bake the cake. Bake for 35-40 mins or until a toothpick comes out clean. Remove from oven and set aside Once cooled, level the top of the cake while still in the pan.
Step 3 - Make ganache. Add heavy cream to a microwave safe bowl and heat in the microwave for 40 seconds. Pour on top of the butterscotch and let rest about 7-9 mins. Stir until ganache begins to form. (if all chips are not melted, microwave again for 10 more seconds, stir and let cool) Add to piping bag.
Step 4 - Make the frosting. Add butter and shortening in a bowl and mix until smooth. Add in the half the powdered sugar and ¼ cup cream soda and mix until smooth. Add remaining powdered sugar and ¼ cup cream soda. Mix until combined, then mix on HIGH until fluffy (about 4-5 mins).
Step 5 - Stack the cake. Add a dollop of buttercream to the cake board. Place down the first layer, cut side up. Add buttercream and spread out on the cake. Add a drizzle of the butterscotch ganache to the frosting. Top with the second layer of cake, cut side down.
Step 6 - Frost the cake with the buttercream. Add thick layers of buttercream to the cake all the way around. Use a cake comb to create the pattern on the side of the cake and a circle pattern on top of the cake until no cake is seen through the frosting. (this also removes excess buttercream).
Step 7 - Add butterscotch drips. Add the drip to the outside rim of the cake (a little goes a long way).
Step 8 - Add rosettes on top of cake. Add remaining buttercream to a piping bag fitted with a tip 1M. Add rosettes around the top of the cake and immediately add sprinkles.