Halloween Sprinkle Geode Cake

Halloween Sprinkle Geode Cake

Bored with the classic 'frosting swirls with sprinkles' cake decor? 

Then I have a perfect cake idea for you - this Halloween Sprinkle Geode cake! It's a take on the endlessly-trending geode cake - but made with sprinkles! 

After making a couple of more traditional-style geode cakes (and finally getting one to turn out), I’m finally also jumping on the sprinkle geode bandwagon! But I put a Halloween twist on this one with a black, purple, and green sprinkle mix and candy melt skulls. Black cocoa cream cheese buttercream means the cake looks stunning and ALSO tastes incredible! The black cocoa also won't stain your teeth the way black-gel-color-buttercream can. 

Obviously the sprinkle mix and skulls make this one a perfect Halloween design - but a different sprinkle mix could turn this into a perfect cake for any occasion! 

Sprinkle geodes are SO fun, and honestly they make for much easier cakes to cut into and eat! (Who really actually likes crunching down on rock candy in their cake slice?)

Recipe + instructions 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!) 

Halloween Sprinkle Geode Cake

The endlessly-trendy geode cake - but made with sprinkles! This Halloween Sprinkle Geode Cake beats trying to chew rock candy any day!
Prep Time30 minutes
Cook Time37 minutes
Decorating time1 hour
Total Time2 hours 7 minutes
Course: Dessert
Cuisine: American
Keyword: Halloween Cake, Halloween cake recipe, Halloween Geode Cake, Halloween Sprinkle Geode Cake
Servings: 16 servings
Calories: 778kcal



Cake layers

Black Cocoa Cream Cheese buttercream


  • Sprinkle mix of your choice (I used FancySprinkles’ ‘Goosebumps’ Halloween mix)
  • Edible silver leaf (Optional; I bought mine from Gold Leaf Factory via Amazon)
  • Candy melts (colors are up to you; I used Wilton purple and green)
  • Edible glitter (optional; I used FancySprinkles’ Prism Powder)


Cake layers

  • Preheat oven to 350°F. Line three 8-inch cake pans with parchment rounds, and /or grease with non-stick or baker’s floured cooking spray.
  • Mix together all dry ingredients (flour, baking powder, sugar, and salt) in a stand mixer with a paddle until fully combined. Add chunks of room-temperature butter into the dry mix, on a low speed. Continue to mix until no large chunks of butter remain, and the mixture becomes crumbly.
  • Pour in eggs and mix on low until just incorporated. Mix in the buttermilk, keeping the mixer speed on low. Add in vanilla and gel color, 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.
  • Bake for 34-37 minutes if using 8-inch pans (or until a toothpick comes out clean). Allow cake layers to cool for 10-15 minutes before removing from pans. Cool completely before frosting. Set in the fridge or freezer to accelerate the cooling process if desired. (This is a great time to make your frosting!)
  • When 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 first, or they may crumble or break.

Black Cocoa Cream Cheese buttercream

  • 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, food color, and salt if needed and beat until well combined.
  • (Note – frosting’s color will deep if left to sit for several hours or overnight – this lets you get a deeper color with less gel food coloring!)


  • Place a smear of frosting on your large cake circle (to keep the cake from sliding while you decorate it) and center your large 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 tiers 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 a large offset spatula and pastry cutter/bench scraper for this part.

Now the fun part - carving the 'Geode' shapes!

  • Carve a geode shape from the side of the cake with a small knife - I picked two points; one a few inches into the top and the other 1” from the cake base for the ends, and made two cuts connecting those points. I made the opening deepest toward the center, probably 1 ½” at its deepest. I also cut a couple smaller geode shapes on either side of the largest one. (Feel free to eat the cake scraps!)
  • With a small offset spatula, re-crumb-coat the geode ‘holes.’ This will keep crumbs in and hold your sprinkles in place.
  • Press sprinkles into the frosting to cover the base of the geode ‘hole.’ I found tweezers and spreading crisco on a fingertip handy for reaching the deeper parts. I also found it easiest to place the larger sprinkles first and then fill in around them with smaller sprinkles.
  • Rim the outside of the geode with bits of edible silver leaf – I tried a few methods for transferring it, because it’s fragile and a bit finicky. Tearing off and moving bits at a time with a dry paintbrush has been my favorite method so far!

Candy skulls (optional)

  • Melt a handful of candy melts (30-50% power in the microwave works well) and transfer to the skull mold; refrigerate 5-10 minutes to set before removing.
  • Finish the cake off with colored skulls on top, and a few extra pieces of silver leaf if you’d like – and you’re done!
  • Seriously; find someone to give you a high-five on your kick-butt cake! DM me on Instagram if you can’t find someone quickly!



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


Serving: 1serving | Calories: 778kcal | Carbohydrates: 100g | Protein: 9g | Fat: 38g

Mentioned in post -
Black Cocoa Cream Cheese Buttercream

Did you make this Halloween Sprinkle Geode Cake?

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