This epic Valentine's Day 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!
What is a Fault Line Cake?
I made this Valentine's Day Fault Line Cake for my family when we all got together the day prior to the big V-Day to watch the Super Bowl. And I thought, what better way to say "I love you" than showing up with an epic layer cake in my hands!?
I first learned about fault line cakes from Cupcake Jemma, and I had been wanting to try one forever.
A 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.
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*
I picked up a box of fondant from my local grocery store and went to town. Fondant can be made at home, but at least I had enough sense of time to buy it pre-made. If you've never worked with fondant before, it's basically a sugar paste that looks and feels like soft polymer clay.
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, so I left it like that. Then I made a heart template from paper and used that to cut out heart shapes from the rolled-out fondant.
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, a gigantic Harry-Potter themed gingerbread house, and an itty bitty gingerbread village.
But for whatever reason, this batch of royal icing would not cooperate! It was too wet and kept spreading into blobs of icing. I left it in the mixing bowl to dry out a bit, which made it easier to pipe into letters and shapes onto the fondant hearts.
Sprinkles!!
I love sprinkles, but I've rarely used them before. 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.
Smooth as Buttercream
I made a classic vanilla buttercream and dyed it purple with food coloring. I figured purple frosting and pink sprinkles looked the best for a Valentine's Day Fault Line Cake, without looking too cheesy.
You can add flavoring your buttercream too, if you wanted to get extra fancy with your cake. I flavored my base layer of buttercream with peanut butter powder.
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!
Chocolate Cake + Peanut Butter Frosting
To construct this layer cake, I made two individual 8-inch round cakes from my favorite rich yet fluffy chocolate cake. I cut each one in half lengthwise so that it formed a total of four cakes.
And the frosting in between the chocolate layers is peanut butter buttercream. I used Martha Stewart's recipe for a lighter peanut butter frosting, which uses peanut butter powder. And come on, chocolate plus peanut butter is one of the best combinations ever!
If you make this Valentine's Day fault line cake, let me know! I had a lot of fun making this cake, and I had even more fun eating it with all my family. Enjoy!!
More Delicious Cake Recipes
- Light and Sweet Date Cake
- Lavender Chocolate Cake
- Homemade Wedding Cake
- Carrot Cake with Buttercream Frosting
- Scrumptious Strawberry Lemon Cake
- Semolina Cake (Basbousa)
- Buche de Noel (Yule Log Cake)
- Miniature Gingerbread House Cake
Tasty Cupcake Recipes
Valentine's Day Fault Line Cake
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!!
Yum-number1
This looks sooo coool!! It takes so much effort to do that so great job!
strawberryandcream
Thank you so much for your kind words! It was a lot of work lol 😅 But so worth it!!