Halloween Slime Cake

Halloween cakes are *the* absolute best!

I saw a Halloween cake years ago that STILL sticks in my memory. It was black with a simple green drip, and I LOVED the way it looked! Super simple, but such a cool look. 

Not long afterward I also found an Erlenmeyer flask (think tapered-top beaker) on sale at a craft store. That was all it took for me to decide to turn a cake design I already loved into a "science-experiment-gone-wrong" Halloween Slime cake! 😉

Why make this Halloween Slime Cake? 

  • To date (even as I update this post in 2024) - this was and is the EASIEST Halloween cake I think I’ve ever done! 
  • Wanting to make whole recipe super-easy to make, I doctored up a couple of boxed cake mixes for the cake layers. It worked great - that said, a scratch recipe is also linked in the FAQs for all my cake purists. 😉 
  • Everyone LOVED the look and the taste! The black cocoa buttercream frosting probably has a lot to do with that. It disappeared SO fast during taste testing! 
  • If you're unsure about your cake decorating abilities, this is a great one to start with!! No one cares if Halloween cakes are a little messy. This is an especially great design for beginner cake decorators; it's supposed to look a bit of a 'science experiment gone wrong' mess! 

Recipe, tips, and links to everything I used are below!

(Disclosure: As an Amazon associate I may earn from qualifying purchases, and my posts often contain affiliate links. If you click a link and make a purchase, I may receive a commission at no extra cost to you!) 

FAQs:

"You used boxed mixes in this recipe - can I use a scratch cake recipe instead?" 
  • Absolutely! You use my Favorite Vanilla Cake recipe, or even your own favorite white or vanilla cake recipe - just add 3-4 large drops of bright/lime green gel food color to the batter before baking. 
"What if I've never added a drip to a cake before?"
  • Don't stress! I can just about promise you that it's easier than you probably think it is! 🙂 
  • Tip #1 - probably my most important drip tip - make sure you measure your candy melts and heavy cream carefully and accurately! Too much/little of either may affect your drip consistency. 
  • Tip #2 - my second most important tip - I highly *highly* recommend that you try a test drip first! Don't pour the drip mixture over the whole cake until you're pretty confident that you're happy with the thickness / consistency of the mixture.  
  • Tip #3 - heat the drip mixture gently! I've over-cooked it in the microwave a couple times, and if it seizes it gets crumbly and weird and I've never had good luck saving it past that point. Shorter time intervals and 30-50% power will be your friend! 
  • If you need a bit more of an in-depth tutorial, I loved this YouTube tutorial by Sugar&Sparrow when I was new to cake drips! 
"Do I have to make the frosting from scratch?"
  • I  mean, lol as the poster of the recipe obviously I'd recommend it. Homemade frosting will beat the socks off store-bought frosting any day of the week, IMHO. That said though...
  • You sure don't have to if you don't want to! Let me tell you, as a mom of a 1 and 3 year old right now sometimes you have to simplify as much as humanly possible for the sake of your sanity! 

  • You can substitute chocolate store-bought frosting and add black cocoa powder and gel color, though the shade of black may be a little lighter.

  • Store-bought frosting is usually a little thinner than my recipe; add a couple Tablespoons of regular or black cocoa powder at a time until you reach a consistency that spreads and stays in place on the cake well. Voila! 

Annnnd that's it! Happy baking - and Happy Halloween!

Halloween Slime Cake (black cake with green candy melt slime and an Erlenmeyer flask)

Halloween Slime Cake

Sarah H
One of my MOST popular Halloween cake - a bright green drip and a Erlenmeyer flask make the perfect Halloween Slime Cake!
Prep Time 20 minutes
Cook Time 30 minutes
Decorating time 15 minutes
Total Time 1 hour 5 minutes
Course Dessert
Cuisine American
Servings 16 servings
Calories 752 kcal

Equipment

Ingredients
  

Cake layers

Black cocoa cream cheese buttercream

Green Cake Drip

  • 6 ounces White Candy Melts (I used Wilton Bright White)
  • 3 Tablespoons heavy whipping cream (I used an incredibly thick Costco brand; you may need a bit less depending on the thickness of your cream)
  • 2-3 drops lime green gel food coloring (Add last; after candy melts are melted with whipping cream!)

Instructions
 

Cake layers

  • Preheat oven to 350°F. Line three 8-inch cake pans with parchment rounds, or grease with non-stick or baker’s floured cooking spray.
  • Mix together all wet ingredients (butter, egg whites, buttermilk, vanilla, and gel food color) in a large bowl with a mixer or wire whisk. Blend in cake mixes for 30 seconds until moistened, then beat for 2 minutes until well combined.
  • 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.
  • 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 – it helps to run an offset spatula or knife around the perimeter of the pan first. Cool completely before frosting. Set in the fridge or freezer to accelerate the cooling process if desired.

Frosting

  • Beat together softened cream cheese and butter; slowly add in powdered sugar alternating with cocoa powder and milk until frosting reaches desired consistency. Add vanilla, black gel color, and salt if needed and beat until well combined.
  • Once your cakes are cool, level them (if needed/desired). This can be done with a cake leveler or a large serrated knife and a ruler.
  • 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.
  • Add your next cake layer on top, and repeat the process with your remaining cake layers.
  • Now you're ready to crumb-coat . If you're unfamiliar with crumb-coating, it's just what it sounds like – spreading 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 or freezer to set the frosting.
  • This is a great time to make and color your ganache drip(s)!

Cake Drip & Decorations

  • Place heavy cream and candy melts in a microwave-safe bowl (don't add the color yet!) and microwave on 50% power in 30-second intervals until smooth, stirring in between. Once the mixture is completely melted and smooth, add in the gel color and mix until the color is even.
  • Once your ganache has cooled to a moderate temperature - it should be liquid but not hot so it doesn't melt your frosting - transfer it to a squeeze bottle or piping bag. You can use a spoon; it just won't give you quite as much control. 
  • Slowly drizzle candy melt ganache around the upper edge of your cake, pausing every inch or so to let more fall in a drip down the side of the cake. Pour a bit of ganache into the Erlenmeyer flask and set it on top of the cake. Smooth any gaps or bumpy spots with a small offset spatula. Place the cake into the refrigerator to set the drips!
    And you’re done! Cut in and enjoy!

Video

Notes

Please note nutrition information is an estimate and may not be exactly accurate. 

Nutrition

Serving: 1sliceCalories: 752kcalCarbohydrates: 98gProtein: 9gFat: 38g
Keyword Halloween cake, Halloween Slime cake
Tried this recipe?Let us know how it was!

Related: 

Black Cocoa Cream Cheese Buttercream

 

Did you make this recipe? Let me know how it went – or make my day and find me on Pinterest or on Instagram and tag @IntensiveCakeUnit in your photo!

6 thoughts on “Halloween Slime Cake

  1. What kind of black coloring do you use or recommend that will not make my coworkers teeth mouth or tongue black.

    1. Hi Debbie! Unfortunately, I have yet to find a black food color that doesn’t leave *some* trace of color behind. My favorite is Americolor’s black gel color – it’s never turned my teeth black, just turns your tongue a bit purple 😉. I just updated this recipe to reflect my new favorite trick though – starting with a dark chocolate frosting made with black cocoa powder allows you to get to a pretty deep black without staining everyone’s mouths much at all! 😉🖤🖤🖤

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