Directions for Cake
Preheat the oven to 350 degrees. Prep 6" cake rounds with a wipe of shortening and dust of flour. Set aside. In a medium bowl, whisk together the buttermilk, sour cream, vegetable oil, egg whites, vanilla, bubble gum extract until combined. Sift in white cake mix and stir until just combined. Divide batter in half in two bowls, add in pink coloring to one bowl. Using a small cookie scoop or spoon, add in one scoop of white batter, one scoop of pink batter, alternating until batter has been divided between all three cake rounds. Bake for 25-27 minutes until center is baked through (don't overbake!). Remove from oven, let cool in pan for 5 minutes, then flip out onto a cooling rack until room temperature.
Directions for Buttercream
In a stand mixer fitted with a paddle attachment, whip up butter for about a minute until light and fluffy. Scrape down the sides of the bowl. Add in salt, vanilla, bubble gum flavoring, and heavy cream until combined. Slowly add in powdered sugar, about a half cup at a time. Add in more heavy cream if needed for a thinner consistency. Whip on high for a minute to create a soft buttercream.
Directions for Ganache Drip
In a small glass bowl, add in chocolate melts and heavy cream. Microwave for 30 seconds, then stir with a small whisk. Add to a squeeze bottle for ganache drip on the side of the cake.
On a cake turntable, place a cardboard round on top (8" round). Add on a small amount of buttercream, spread it around to act like "glue" for holding the cake onto the board. Place on first cake round, add on about a cup of buttercream, spread it flat with an offset cake spatula. Add on next layer and repeat with remaining two layers. Crumb coat the cake, place in the fridge to set, then add on final coat. Add sprinkle rim on the bottom, freeze a second to set, then add on ganache drip and sprinkles. Top with gumballs.