Preheat your oven to 350 degrees F. Prepare three 8-inch or four 6-inch round cake pans by spraying each pan with non-stick spray, covering the bottom of the pan with parchment paper and spraying the parchment paper with the non-stick spray as well. Set aside.
In a medium-sized mixing bowl, combine the whole egg, egg whites, vanilla extract and root beer flavor. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, combine the cake flour, sugar, baking powder and salt. Mix on low speed for about 30 seconds.
With the mixer on low speed, add the butter and root beer. Continue to mix on low until just combined and then increase to medium speed and mix for 1 minute.
Scrape down the sides of the bowl and add the egg mixture in two additions, beating on medium speed after each addition until just combined and all the ingredients are thoroughly incorporated.
Divide the batter into the three prepared cake pans, using a kitchen scale to measure equal parts in each pan. Bake for 20-25 minutes (my cakes took 20 minutes), or until a toothpick inserted into the center of the cake comes out clean.
Let the cakes cool in the pans for 10 minutes and then invert onto wire racks until completely cool.
For the Buttercream
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed for about 2 minutes, until light and fluffy.
With the mixer on low speed, slowly add the powdered sugar, followed by the heavy cream, vanilla extract and root beer flavor.
Continue to beat the frosting on medium speed for an additional 5-7 minutes, until the mixture has lightened in color and texture.
Before frosting your cake, make sure to use a wooden spoon to beat the frosting by hand to push out any air pockets.
For the Drip
If you use the root beer baking chips, heat your cream in the microwave for about 30-40 seconds. Pour the cream over the baking chips and let sit for about 5 minutes. Stir the mixture until smooth. If there are still chunks of baking chips, microwave the mixture for 10 seconds and stir again. Let cool slightly before pouring on your cake.
If you use white chocolate chips, heat your cream in the microwave for about 30-40 seconds. Pour the cream over the baking chips and let sit for about 5 minutes. Stir the mixture until smooth. If there are still chunks of baking chips, microwave the mixture for 10 seconds and stir again. Add the root beer flavor and stir again. Let cool slightly before pouring on your cake.
For the Whipped Cream
Combine all the ingredients in the bowl of a stand mixer fitted with the whisk attachment. Whip on high until stiff peaks form.
Level each of your cake layers with a cake leveler or serrated knife. Slather a small amount of frosting on your cake board to hold your cake in place.
Place the first cake layer, top side up, on the cake board and spread about 1 cup of frosting on top. Drizzle about 1-2 tablespoons of the drip on top of the frosting and spread evenly.
Repeat step 2 with the second cake layer.
Place the final cake layer, top side down, on top of the frosting and drip. Cover the entire cake with a thin coat of frosting to lock in the crumbs. Freeze the cake for about 10 minutes to set the crumb coat.
Apply the rest of the frosting and top with the root beer drip, whipped cream, and garnishes.
If you don’t plan to eat the cake right away, hold off on adding the whipped cream, and freeze the cake in an airtight container. Allow to thaw for about 6 hours before serving. Add the whipped cream and garnishes before serving.
Recipe by Cake by Courtney at https://cakebycourtney.com/root-beer-float-cake/