Rainbow Surprise Inside Cupcakes

St. Patrick’s Day is among us and I’m feeling really lucky. I may not have the best Irish accent, but I collaborated with Donal Skehan for an awesome St. Patrick’s Day video. Check out his Chocolate Guinness Cake. Here on My Cupcake Addiction, I’m going to be showing you how to make Rainbow Surprise Inside Cupcakes!

For this cake, you’ll want my perfectly pipeable buttercream frosting. You can find that recipe here. For this cake, I actually strongly recommend using a box cake. With any rainbow cake, you want to use box cakes because there’s a lot of mixing. Home made cakes are easier to have the air knocked out of, but box cakes hold up just fine. Helpful tip: DO NOT overfill the cupcake liners with batter! It’ll cause the rainbow circle to rise to the top.


  1. Preheat a moderate oven (175°C/350°F)
  2. Combine box cakes, eggs, milk, and butter an electric mixer, and beat until mixed.

    cake batter mix
  3. Once mixed, divide half of the batter into the six small bowls. This should be about three generous tablespoons in each bowl.
  4. Add a fair amount of food color and mix well.

    color dye batter
  5. Transfer all the colored batter into their own individual snap seal bags. Then, use a pair of scissors to cut a generous corner from each snap seal bag.
  6. Pipe colorful stripes in red, orange, yellow, green, blue, and purple batter onto a baking sheet line with parchment paper. Repeat along this piping order along the entire baking sheet. Then, add a second layer of batter directly on top of your first layer of batter.

    rainbow sheet cake
  7. Cook sheet cake in a moderate oven for 15 minutes, or until the center of the cake springs back.
  8. Freezer for at least an hour.
  9. Once frozen, remove sheet cake from the baking sheet, and peel back the parchment paper away from the cake.
  10. Use a serrated edge knife to trim away the brown parts of the sheet cake.
  11. Use a circle cutter to cut out neat rainbow circles from the sheet cake.

    circle cutter rainbow

    Optional: color the remainder of your cake batter bright green (you can also leave the batter white)
  12. Spoon cake batter into the bottom of each cupcake liner (about 1 tablespoon). Then, place the rainbow circles into each cupcake liners so that they are standing on their sides. Then, transfer the rest of the batter into a snap seal bag, and cut off a fine corner tip. Fill the rest of the cupcake wrapper so that it just covers the top of the rainbow circle. DO NOT OVERFILL!

    batter rainbow
  13. Place in a moderate oven for about 11 minutes.
  14. Use a pair of scissors to cut out rainbows from the template. Tape the rainbow onto a toothpick.
  15. Once the cupcakes are done, remove from the cupcake ray and let them cool on a cooling rack.
  16. Place rainbow sprinkles into a small bowl. Brush on Luster Dust, and mix for about 5 minutes so that all the sprinkles are completely coated.

    gold dust
  17. Place green buttercream frosting into a snap seal bag. Pipe a rough swirl onto the top of the cupcakes. Then, use a knife to smooth out the frosting and spread them to the cupcake liners.
  18. Create a grass effect on the cupcakes by piping rough, quick blobs onto the cupcake (you can also use a grass piping tip on a piping bag). Leave the top most part of the hill without grass frosting.

    piping grass
  19. Sprinkle shamrocks around the base of the grass. Then, a small spoonful of golden sprinkles. Place a rainbow toothpick in the center.

    rainbow inside final

I wouldn’t mind finding these cupcakes at the end of a rainbow! A pot of gold wouldn’t be too bad either 🌈

-For the printable recipe click here: http://bit.ly/2hqbZHF

What You’ll Need:  

  • 2 box cakes
  • 4 eggs
  • 2 cups of milk
  • 2 sticks of butter
  • Food dyes (red, orange, yellow, green, blue, purple,)
  • Buttercream frosting (bright green!)
  • Round confetti sprinkles
  • Irish Shamrock sprinkles
  • Gold Luster Dust

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