Once cake layers are cool, use a cake saw or serrated knife to cut off any domed tops. This will help create an even and flat layer of cake.
Place one cake layer on your cake stand or cake plate and spread a layer of frosting on top. Repeat with remaining cake layers. Spread frosting over the outside of the cake. (I added a tiny bit of pink food coloring to some of my buttercream and added some swipes of pink frosting as well.)
Chill the cake in the refrigerator for 20 to 30 minutes. Transfer the white chocolate mixture to a piping bag or squeeze bottle.
When you’re ready to add the drip, remove the cake from the refrigerator and pipe drips around the edges of the cake. I like to add the drips around the edges, which creates a border and leaves the top open. Then I go back and fill in the top by drizzling on some of the white chocolate mixture and using an offset spatula to spread it out to the drips around the edges. Personally, I prefer doing it this way, but you could start by pouring some of the white chocolate mixture onto the top of the cake, spreading it just to the edges, and then adding the drips around the sides.
Let the drips set for a few minutes. Then add any additional decorations or sprinkles as you like!
Cake can be stored covered at room temperature or in the refrigerator.