Preheat oven to 350°F. Prepare three 8-inch cake pans with baker's floured cooking spray, or grease and line with parchment rounds.
Mix together all dry ingredients (flour, sugar, baking powder, and salt) in a stand mixer with a paddle until fully combined.
Mix bits of room-temperature butter into the dry mix, on a low speed. Continue to mix until no large chunks of butter are visible, and the mix looks crumbly.
Pour in eggs, and mix on low until just incorporated. Add in the buttermilk on a low speed. Add in oil and vanilla, and mix at a low speed until fully incorporated. Scrape down the sides of the bowl with a spatula, then beat on medium speed for about 30 seconds.
Divide batter evenly between the prepared cake pans (I find a kitchen scale helpful for this part). This guarantees your layers will bake to be the same height. Add colored sprinkles to your cake batter – if you’d like to add a little color to your layers – and marble them in with an offset spatula or knife.
Bake for 35-37 minutes (or until a toothpick comes out clean). Allow cake layers to cool for 10-15 minutes on a wire cooling rack before removing from pans. Cool completely before frosting. Set in the fridge or freezer to accelerate the cooling process if desired.
Once the layers have fully cooled, they can be leveled and any caramelized bits can be trimmed from the sides / top of the cake using a serrated knife if desired. Be sure the layers are completely cooled or chilled before trimming. If you try to trim the layers while they’re still warm, they will crumble and break.
Cream Cheese Buttercream Frosting
Beat together softened cream cheese and butter; slowly add in powdered sugar alternating with whipping cream until frosting reaches desired consistency. Add vanilla and salt if needed and beat until well combined.
Assembly
Place a smear of frosting on your cake circle (to keep the cake from sliding while you decorate it) and center your first cake layer in the center of the circle. Spread the layer with frosting and toss on some more sprinkles if you’d like. Repeat the process with the next layer and add your last cake layer on top. (I put my top layer on upside-down to make shaping the frosting on top of the cake easier.)
Now you're ready to crumb-coat. If you're unfamiliar with crumb-coating, it's just what it sounds like - a thin layer of frosting over the entire outside of the cake to keep crumbs out of your final layer.
Once your crumb coat has set (this takes about 5-10 minutes in the fridge), add your final layer of frosting and smooth. I like to use an offset spatula and bench scraper for this part. Once your cake is covered, place it into the fridge so it's cold enough to set your drip.
Cake Drip(s)
Combine heavy cream and white chocolate in a microwave-safe bowl. Microwave on half-power in 30-second intervals until melted and smooth, stirring in between.
Divide white chocolate mixture into four small bowls and color purple, green, yellow, and orange. (I don’t recommend liquid coloring; it can make the white chocolate seize and harden.)
Decorating
Okay! Now that all the pieces are ready, it’s time to decorate your cake! I recommend a test drip - your cake drip mixes should feel slightly warm and be liquid; too cold and they won't drip, but if they're too hot it might melt your frosting.
I started with the flask since it was the biggest, and piped some ganache into the inside before I set it on top of the cake, letting it run out onto the top of the cake once I set it down. With a piping bag, add more ganache around the opening of the beaker to the cake edge, letting it run over in several drips.
Repeat with test tubes, adding them at various angles around the cake so there are several drips coming off the sides. I used one smaller test tube set straight up in the cake with ganache coming out the top, and another larger test tube with a ‘sprinkle explosion’ coming out the top and over the top and down the side of the cake.
I’ve added pictures to give you some ideas, but feel free to take creative liberties with this part!
Refrigerate until ready to eat - and enjoy!
Video
Notes
Please note nutrition information is an estimate and may not be exactly accurate.