The cutest celebration cake has arrived. By turning a playful treat—classic Rice Krispies—into a layered cake, I created a Funfetti Rice Krispies Treat Cake that makes any party feel extra special. It’s colorful, nostalgic, and soft like cake while still tasting like those beloved marshmallow cereal bars.
Rice Krispie Treats… but make it funfetti
I adore a warm, gooey Rice Krispie treat. They’re quick to make and endlessly customizable for birthdays, showers, or any celebration. With marshmallows, butter, and cereal as a base, they’re a family favorite. For this cake I wanted those exact nostalgic flavors—plus sprinkles—without simply stacking Rice Krispie layers as the whole cake. The result is a soft, tender cake that still captures the cereal’s sweet charm.
Infused flavors
I didn’t want to use the actual compacted Rice Krispie treat layers for the cake itself, although you can if you prefer—just shape the treats into cake pans and stack. Instead, I focused on bringing the cereal flavor into both the cake batter and the frosting. Two simple techniques make that possible: a cereal soak to flavor the wet ingredients, and powdered cereal folded into the buttercream for clear cereal notes.
Cereal-soaked milk (cereal milk) method
To reproduce that classic bowl-of-cereal flavor, I soaked Rice Krispies in buttermilk, letting the cereal infuse the liquid for about 15–20 minutes. Think of the sweet milk left in the bowl after you finish your cereal—that’s the flavor we want. Using that soaked buttermilk in the batter gives the cake an unmistakable Rice Krispie tone without relying on whole cereal pieces in the crumb.
Powdered cereal in the buttercream
For the frosting, I pulsed Rice Krispies into a fine powder and stirred it into a marshmallow-forward buttercream. The powdered cereal blends smoothly into the butter and sugar, leaving tiny specks that you can see and, more importantly, taste. This step ensures the frosting echoes the cake’s cereal flavor and amplifies the Rice Krispie profile with every bite.
Tip: Pulse the cereal until it becomes a fine powder. That prevents clogging when you pipe the frosting and keeps the buttercream silky and easy to spread.
I made a little experiment: I gave my husband a blind bite and asked him to guess the flavor. He was amazed—it really does taste like Rice Krispie treats, but with the texture and tenderness of cake. If you want a reliable celebration cake that’s playful and nostalgic, this Funfetti Rice Krispies Treat Cake is a perfect pick. It’s vibrant, fun, and surprisingly true to the original treat.
I can’t wait for you to try this one. If you give it a go, I’d love to see your version—tag me @bakingwithblondie so I can share in the fun. Happy baking!
xo,
Mandy
Get the Recipe:
Funfetti Rice Krispies Treat Cake
Ingredients
Funfetti Rice Krispie Cake Batter
- 1 cup buttermilk, room temperature
- 2 cups Rice Krispies cereal, divided (1 cup for the cereal soak, 1 cup pulsed to powder for the batter)
- 4 egg whites, room temperature
- 2/3 cup sour cream, room temperature
- 1/3 cup vegetable oil
- 1 Tablespoon vanilla
- 1/4 cup rainbow jimmies
- 1 (15.25 oz) box white cake mix
Rice Krispie Treat Buttercream
- 1 1/2 cup (three sticks) unsalted butter, slightly softened
- 3 cups Rice Krispies cereal, pulsed to a powder (about 3/4 cup powdered cereal after pulsing)
- 1 cup marshmallow fluff
- 1 pinch salt
- 1 Tablespoon vanilla
- 1/4 cup heavy cream, plus more if needed
- 7–8 cups powdered sugar
Rice Krispie Treats (optional for decorating)
- 4 Tablespoons unsalted butter
- 4 cups small marshmallows
- 6 cups Rice Krispies cereal
- 1/2 cup rainbow jimmies
Garnishes
- 1/2 cup Rice Krispies cereal
- 1/2 cup rainbow jimmies
Instructions
For the Funfetti Rice Krispie Cake Batter
- Stir 1 cup Rice Krispies into the buttermilk in a small bowl and let soak 15–20 minutes. The longer it soaks, the stronger the cereal flavor.
- Preheat the oven to 325°F on convection (add a few minutes for a conventional oven). Prepare three 6″ cake pans—or two 8″/9″ rounds—by greasing or dusting with flour. Set aside.
- In a large bowl, add the cereal-soaked buttermilk (including the soggy cereal), the pulsed powdered Rice Krispies, egg whites, sour cream, vegetable oil, and vanilla. Stir in the rainbow sprinkles and sift in the cake mix. Divide the batter evenly between the prepared pans and bake 25–27 minutes, until centers are set. Cool on wire racks, wrap, and chill or freeze overnight for easier assembly.
For the Rice Krispie Treat Buttercream
- In a stand mixer fitted with the paddle, beat the butter until light and fluffy. Add the powdered cereal, marshmallow fluff, vanilla, salt, and heavy cream. Mix on medium until combined, scraping the bowl as needed. Gradually add powdered sugar, about 1/2 cup at a time, until desired sweetness and texture are reached. If needed, add more heavy cream by the tablespoon. Beat on high briefly until the buttercream is smooth and airy.
For the Funfetti Rice Krispie Garnishes
- Line a 9×13 pan with plastic wrap or lightly spray it. In a large pot over medium heat, melt the butter, add marshmallows, and stir until melted. Stir in the cereal, then fold in rainbow jimmies. Press into the pan and let cool. Cut into cubes to use as cake toppers or decorations. Expect leftovers for snacking.
Assembly
- Place a small dab of buttercream on a cake board and set the first cake layer on it. Spread a layer of the Rice Krispie buttercream, then add the second layer, and repeat with the final layer. Crumb coat the cake and freeze briefly to set.
- Apply a final smooth coat of buttercream using an offset spatula and cake scraper for clean edges. Decorate the sides and top with extra sprinkles and a few Rice Krispie pieces.
- Pipe small buttercream dollops around the top rim with a Wilton 6B or 8B tip and top each with a mini Rice Krispie cube.
- Serve and enjoy!