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Home » Recipes » Layer Cakes

Sprinkles Fault Line Cake Tutorial

Published: Feb 22, 2022 · Updated: Sep 18, 2025 by Carissa Erzen · This post may contain affiliate links · 3 Comments

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5 from 1 vote

This epic sprinkles fault line cake is full of rich chocolate cake and creamy peanut butter frosting! The icing and sprinkles create a design that mimics a fault line, as if the glittery sprinkles are bursting forth from this delicious cake!

Valentine's Day Fault Line Cake topped with white paper hearts and fondant purple hearts

I first learned about fault line cakes from Cupcake Jemma, and I had been wanting to try one forever. It looks epic and it tastes delicious since I made this version with chocolate cake and peanut butter frosting.

This sprinkles fault line cake was inspired by my other stunning layer cakes including lavender chocolate cake, German Black Forest cake, a homemade wedding cake, and scrumptious strawberry lemon cake.

a fault line sprinkle cake with a slice cut out and placed in the background on a pink plate

What is a Fault Line Cake?

I made this Valentine's Day Fault Line Cake for my family! And I thought, what better way to say "I love you" than showing up with an epic layer cake in my hands!?

A sprinkles fault line cake mimics what a fault line looks like on the Earth's surface.

Except this one is edible, since it's made out of buttercream and sprinkles instead of rocks. To me, it looks as if the frosting of the cake is bursting open to reveal the sparkling precious gems (aka sprinkles) beneath the surface.

a white cake stand topped with a purple and pink Valentine's Day Fault Line Cake

How to Make a Sprinkles Fault Line Cake

  1. Layer the cake and buttercream: Place your first chocolate cake layer on a cake stand or serving plate.
    Spread the peanut butter buttercream frosting on top of this first cake layer, until it's about ½-inch thick.
    Place the second cake layer directly on top, and spread more peanut butter buttercream on top. Repeat with the third and fourth cake layers.
  2. Frost the sides: Spread the remaining peanut butter buttercream on the sides and top of the cake in a thin layer to make the crumb coat.
    Refrigerate for at least 30 minutes.
  3. Add the sprinkles: Spread purple buttercream frosting along the sides of the cake, just in the middle-third section.
    Then immediately use your hand to pat sprinkles onto the wet buttercream.
    Refrigerate the cake for another 20 minutes.
  4. Finish decorating: Spread the rest of the purple buttercream on the top and bottom-third and top-third of the sides of the cake. The frosting should just barely overlap the sprinkle line.
    Refrigerate for another at least 30 minutes to set. Slice and enjoy!!
a hand using a pallet knife to smooth out vanilla buttercream onto a Valentine's Day Fault Line Cake

Tips on Using Fondant

I don't know about you, but sometimes I get into the mode of a ridiculous optimist. I figured, if I'm already trying a brand new technique that looks difficult and time consuming, why not try TWO new decorating techniques at the same time!? How hard can it be?? *foreshadowing*

If you've never worked with fondant before, it's made of sugar paste that looks and feels like soft polymer clay.

  • Use Store Bought Fondant: I picked up a box of fondant from my local grocery store and went to town. Fondant can be made at home, but I find it way easier to buy it pre-made.
  • Colors: I added a few drops of purple food dye and began kneading the color into some of the fondant. As I kneaded it, it started to take on this gorgeous marble or tie-dye effect.
  • Shapes: I made a heart template from paper. Then I used that template to cut out heart shapes from the rolled-out fondant with a small paring knife.
  • Keep it Dry: Ensure your work surface, your hands, and your rolling pin are dry before handling fondant. Any moisture can stick to the fondant and make it too sticky to work with.
  • Powdered Sugar: If your fondant does become too warm or moist, dust a little powdered sugar onto the fondant to prevent it from sticking.
hands cutting heart shapes out of purple fondant

Tips on Using Royal Icing

This was not my first rodeo with royal icing. I've made it before (with varying degrees of success) to decorate sugar cookies, pop tart macarons and a gigantic Harry-Potter themed gingerbread house.

  • Keep it Damp: Royal icing dries out pretty quickly, so keep it either in a piping bag, or covered in a bowl with plastic wrap directly on its surface.
  • Coloring Icing: Use gel or paste food colors to avoid adding too much liquid, which can alter the consistency. Liquid food coloring will make your royal icing too thin and runny.
  • Avoid Overmixing: Overmixing your royal icing can incorporate too much air, which adds bubbles in your icing so it won't be as smooth.
  • Use Piping Bags and Tips: Invest in good-quality piping bags and a variety of tips or nozzles to be able to decorate with different designs.
  • Drying Completely: Allow your royal icing designs on the sprinkles fault line cake to dry completely. Depending on the humidity and thickness, this could be anywhere from a few hours to overnight.
hands piping white royal icing onto fondant hearts
close up of a fondant heart decorated with white royal icing stuck on the side of a fault line cake

Tips for Decorating with Sprinkles

I love sprinkles! It's like edible glitter confetti! I mixed several different types of sprinkles together so there was a variety of shapes, sizes and shades of pink and white.

Pro Tip #1: When you're decorating with sprinkles, I recommend to put a large baking sheet underneath. This will help catch all the sprinkles that don't stick to the icing, so it'll make clean-up way easier.

Pro Tip #2: As soon as you frost the middle section of your cake, slap on those sprinkles. The sprinkles will stick best to wet frosting. If it's allowed time to dry, the sprinkles will just fall off.

a hand holding pink and white sprinkles over a bowl of more sprinkles
a hand patting pink and white sprinkles onto a chocolate and peanut butter valentines cake

One of the best parts about a fault line cake is that since it's supposed to look like the cake is bursting open, your frosting doesn't have to be perfect. The rough edges at the top and bottom of the sprinkle line help it look more natural.

If the lines were perfectly straight, it'd just look like a run-of-the-mill layer cake. But this is a fault line cake, my friends! This cake is exploding with sprinkles and flavor and fun!

a purple and pink Valentines Day Fault Line Cake decorated with sprinkles, fondant and royal icing

Storing

Fridge: Cover any exposed cake slices with plastic cling wrap, and store in the fridge for up to 4 days.

Freezer: Wrap the whole cake in plastic wrap then aluminum foil, or store individual slices in airtight containers. Freeze for up to 3 months and thaw overnight in the fridge.

a chocolate cake with peanut butter frosting decorated with pink sprinkles and purple buttercream for valentine's day

Sprinkles Fault Line Cake

Carissa Erzen
This epic sprinkles fault line cake is full of rich chocolate cake & creamy peanut butter frosting! The icing and sprinkles create a design that mimics a fault line, as if the glittery sprinkles are bursting forth from the delicious cake!
5 from 1 vote
Print Pin Recipe Rate Recipe Save Saved Recipe!
Prep Time 50 minutes mins
Cook Time 40 minutes mins
Decorating Time 1 hour hr 30 minutes mins
Total Time 3 hours hrs
Course Dessert
Cuisine American
Servings 12 servings
Calories 999 kcal

Ingredients
  

Chocolate Cake

  • 2 teaspoon white vinegar
  • 1 scant cup milk (dairy or dairy-free, of your choice)
  • 1¾ cups all purpose flour
  • 1¾ cups granulated sugar
  • ¾ cup unsweetened cocoa powder
  • 1 teaspoon fine sea salt
  • 1½ teaspoon baking soda
  • 1½ teaspoon baking powder
  • 2 large eggs
  • 1 tablespoon vanilla extract
  • ½ cup vegetable oil
  • ¾ cup strong, freshly brewed black coffee

Peanut Butter Buttercream (in between the cake layers)

  • 3 sticks unsalted butter, softened to room temperature
  • ⅔ cup peanut butter powder
  • ¼ cup milk (dairy or dairy-free, of your choice)
  • 1 teaspoon vanilla extract
  • ¼ teaspoon salt
  • 3¾ cups powdered sugar

Purple Vanilla Buttercream (to decorate the outsides of the cake)

  • 3 sticks unsalted butter, softened to room temperature
  • 1 teaspoon vanilla extract
  • 2 tablespoon milk (dairy or dairy-free, of your choice)
  • ¼ teaspoon salt
  • 3½ cups powdered sugar

Instructions
 

Make the Chocolate Cake Layers

  • Preheat the oven to 350°F. Grease two 8-inch round cake tins.
  • Pour the two teaspoons of white vinegar and the scant cup of milk in a bowl and let sit for 10 minutes at room temperature to curdle a bit & become homemade buttermilk. Alternatively, you could use one whole cup buttermilk from the store.
  • In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, unsweetened cocoa powder, salt, baking powder and baking soda. Set aside.
  • In another large mixing bowl, whisk together the two eggs, vanilla extract, vegetable oil and your homemade or store-bought buttermilk.
  • Add the wet ingredients into the dry ingredients and mix it with a whisk or spatula until there is no dry mixture visible.
  • Add the hot strong coffee and whisk again until the batter is smooth.
  • Pour half the batter into each of the two cake tins. Bake for 30 to 40 minutes, until a toothpick comes out clean from the center of each cake. (Be sure to check each cake for doneness, as they could finish baking at different times.)
    Let the cakes cool in the pans for 15 minutes, then remove them from the pans and allow to cool to room temperature on a cooling rack.
  • Once the cake is completely cool, trim off the caramelized edges, then slice each parallel to the countertop to create a total of four layers, each about ½ inch thick.

Make the Peanut Butter Buttercream

  • Beat the room-temperature butter in a mixing bowl with an electric whisk or in a stand mixer with a paddle attachment until it is pale yellow and fluffy.
  • Scrape the sides of the bowl then add the peanut butter powder, milk, vanilla, salt and half the powdered sugar. Mix on a low speed until everything is well combined, scraping the sides of the bowl as needed.
    Add the rest of the powdered sugar and mix again until everything is well combined.
    Set aside at room temperature covered with plastic wrap.

Make the Purple Vanilla Buttercream

  • Prepare the vanilla buttercream just like the peanut butter buttercream.
    Beat the butter until it's pale yellow and fluffy. Add the vanilla, milk, salt and half the powdered sugar and mix on low until combined.
    Add the rest of the powdered sugar and mix again until fluffy.
  • Add a tiny bit of purple food coloring and mix on low until you achieve your desired shade of purple.
    Set aside at room temperature covered with plastic wrap.

Assemble Your Fault Line Cake

  • Spread a tablespoon of peanut butter buttercream on a plate or cake stand, then place the first cake layer in the center.
  • Spread the peanut butter buttercream on top of this first cake layer, until it's about ½-inch thick.
  • Place the second cake layer directly on top, and spread more peanut butter buttercream on top. Repeat with the third and fourth cake layers.
  • Spread the remaining peanut butter buttercream on the sides and top of the cake. It doesn't have to be thick - just enough to lock in all the cake crumbs.
    Let it set it the fridge for at least 30 minutes.
  • Place the cake in the center of a baking sheet (to catch any sprinkles that fall off).
  • Spread the purple vanilla buttercream along the sides of the cake, just in the middle-third section. Then immediately use your hand to pat sprinkles onto the wet buttercream.
  • Return the cake to the fridge to set for another 20 minutes, to make sure the sprinkles don't fall off when you add the rest of the frosting.
  • Spread the rest of the purple buttercream on the top and bottom-third and top-third of the sides of the cake. The buttercream on the sides should just barely overlap the sprinkle line. Keep the edges jagged to look more natural.
  • It's easiest to slice when pulled straight from the fridge after allowing the top layer of buttercream to set for at least 30 minutes. Enjoy!!

Nutrition

Serving: 1sliceCalories: 999kcalCarbohydrates: 121gProtein: 7gFat: 58gSaturated Fat: 31gPolyunsaturated Fat: 7gMonounsaturated Fat: 15gTrans Fat: 2gCholesterol: 150mgSodium: 546mgPotassium: 148mgFiber: 3gSugar: 101gVitamin A: 1487IUCalcium: 72mgIron: 2mg
Keyword fault line cake recipe, sprinkles fault line cake
Did you make this recipe?Leave a comment below - I love hearing from you!

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About Carissa Erzen

Growing up in Germany, I fell head-over-heels in love with ALL the German baked goods, from Lebkuchen to pretzels. Now I'm the founder, recipe developer, and food photographer behind Humbly Homemade, where I test and share German sweets lovingly created from scratch. So pull up a chair, and stay a while!

Reader Interactions

Comments

  1. Yum-number1

    February 25, 2022 at 1:24 pm

    This looks sooo coool!! It takes so much effort to do that so great job!

    Reply
    • strawberryandcream

      February 26, 2022 at 1:56 pm

      Thank you so much for your kind words! It was a lot of work lol 😅 But so worth it!!

      Reply
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I'm the founder, recipe developer, and food photographer behind Humbly Homemade. Inspired by my childhood growing up in Germany, I share recipes of delicious German bakes from scratch.

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