An entire cake covered in sprinkles can be done in a snap, and it really takes just a couple little tricks to easily get the job done. For St. Patrick’s Day this year, I wanted to create a rainbow striped cake with a bit of different flair than the usual buttercream stripes, and this cake definitely delivered something fun and unique. You can always add on some dollops of buttercream on top, or fun rainbow cake toppers to add to the sprinkle cake base. This cake is also not just for St. Patrick’s day, but for any rainbow-lover at heart throughout the year.

Today I’m going to walk you through the steps of getting these gorgeous stripes on the inside (very Lisa Frank-looking, don’t you think?) as well as the outside stripes with those tiny rainbow nonpareils sprinkles. Let’s dive right in, shall we?

Bake your cake. I used my Dark Chocolate Cake that I originally paired with my Peanut Butter Buttercream (still my husband’s favorite cake to this day, no joke. I baked three 6″ cake rounds, then sliced them in half so I have 6 skinny rounds to layer together for this cake. The dark cake layers really made the bright rainbow buttercream pop!

Freeze your cake rounds. This really helps ease the stacking and rolling process. A cold cake will not slide around, it will hold it’s shape while stacking the layers tall. To freeze your cake layers, wait until they reach room temperature on a cooling rack after baking, then wrap them up twice in plastic wrap. Freeze for at least a few hours. You want them solid!

Color your buttercream. I made one batch of my Vanilla Bean Buttercream (but used vanilla instead of vanilla bean paste). To tint the buttercream different colors, I separated the buttercream batch into separate little bowls (tupperware works great for this). Using Wilton gel colors or Americolor gel colors is always the best route – I feel like they both can achieve really great colors without having to use a lot of coloring. Add a tiny bit at a time, and stir. Once you go too bright in the color you’re trying to make, it’s tricky to go backwards, so go easy, add a little bit as you go, and stop when you’re almost there. Colors tend to become more vivid with time when it comes to buttercream, so a little is all it takes. I went with pink, orange, yellow, green, and blue this time. I left purple out because, well, we only have 6 cake layers and room for 5 fillings.

Remember: you only need enough colored buttercream to fill the cake layers, so make sure to leave some for the outside of the cake for the crumb coat, and final coat before adding on the sprinkles.

Frost and stack cake on a cardboard round (6″ cardboard taped to a 8″ cardboard round). I used one color per cake layer (filling). Using a piping bag really helps between the layers for an even layer. If you add on the buttercream between the layers with your offset icing spatula, you risk not using enough, or maybe too much, buttercream between the layers. I use disposable piping bags when I’m frosting between the cakes so that I can just toss them afterwards. The cardboard round is essential for the success of this cake, you’ll see later. 😉

Crumb coat cake. After you’ve filled and stacked your cake layers, add a small even layer of buttercream around the entire cake, then FREEZE to set. About 5 minutes is all it takes. You want to keep this cake cold.

Add on final coat of buttercream. We need these rainbow sprinkles to stick, right? Well, buttercream serves as the perfect layer of “glue.” Frost the cake as you would a regular cake layer, but no need to smooth out all the edges, you’re about to so something insane with this cake next…

It’s sprinkle prep time. This is the fun part, the scary part, but also the fun part, but also the scary part… catch my drift? On a cookie sheet, with little color packets (I used Wilton’s individual nonpareils color packets for $1 per color at Michaels Arts & Crafts), carefully spread each color in a long stripe. The nonpareils will want to escape and roll around, but carefully push each color to the side with a cake scraper in a straight line. Repeat with the remaining colors (see video below for a better visual), until you have a rainbow the “height” and “length” of your cake.

GASP! Roll your cake in the sprinkles! Separate your cake from the 8″ round using a cake scraper or cake lifter. Place another 6″ round on the top of the cake, so you have a 6″ cardboard round on top and bottom of the cake. Place your hands on both sides of the cake with the cardboard rounds and gently roll while pressing the cake in the prepared sprinkle rainbow. If the cake is cold, and the buttercream hasn’t set, the sprinkles should stick right away to the cake as you roll it. Roll it a could times as needed, but usually that first roll gets them all stuck to it. That’s it!

I usually add on some sprinkles on top that match whatever color was the top stripe to finish off the cake. So tell, me, are you ready to ROLL? Can’t wait to see your rainbow sprinkle cakes!

Here’s a video of the sprinkle laying and cake rolling process:

Here’s a video above from my Studio 5 segment, too. Make sure to tag #bakingwithblondie or @bakingwithblondie on Instagram for me to see your baking creations! Happy baking!

xo, Mandy