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Peek-A-Boo St. Patrick’s Day Cake

Chocolate loaf cake with green buttercream frosting and rainbow shamrock in the middle.

Peek-A-Boo St. Patrick's Day Cake

I’m so excited to share this cake with you! I love St. Patrick’s Day. My ancestors came from Ireland and my granddad Sullivan used to throw a big St. Paddy’s Day party every year. I’m talking a hundred people or more. It was a big deal and so much fun! Everyone wore green, of course.

My granddad even had a restaurant called The Shamrock in the late 1950s. It was basically a hamburger joint (pre-McDonald’s era). So the shamrock holds a special place in my heart. And the inspiration for this cake. This Peek-A-Boo St. Patrick’s Day Cake is even cuter than I had hoped and perfect for a March 17th celebration.

Peek-A-Boo St. Patrick's Day Cake

My mom and I traveled to Ireland in 2000. It’s such a beautiful country. We rented a car and logged a good 2,000 miles on that thing. Driving on the right side of the car on the left lane of the highway with a stick shift I had to manuver with my left hand was not an easy task for this American! Yikes! Then there were the random herds of sheep crossing the road now and then. That was actually pretty cool.

While we were there, I purchased a book on Irish family names. I found out that my maiden name – Sullivan – is the 3rd most common Irish name after Murphy (#1) and O’Donnell (#2).

My mom and stepdad are accomplished Irish musicians, so the trip was especially fun for my mom. We had a wonderful time!

Peek-A-Boo St. Patrick's Day Cake

The process for making this cake is very similar to the Rainbow Heart Suprise-Inside Cake which I made last year.

  1. Make a white cake mix batter (according to package instructions). Divide batter into 5 bowls and add food color of your choice.
  2. Pour batter into resealable plastic bags.
  3. Clip the corners of the bags and pipe batter in lines on a parchment lined half sheet pan or a 15″x18″ cookie sheet with raised edges.
  4. Bake for 8-10 minutes at 350°F. Use a small shamrock shaped cookie cutter to cut out cake “cookies.”

Peek-A-Boo St. Patrick's Day Cake

Meanwhile, prepare a chocolate cake mix (according to package instructions) and then assemble the cake as follows:

  1. Grease and line a 10″x5″ loaf pan with parchment paper. Pour a little bit of batter in bottom of pan.
  2. Line up cookies, standing up straight and side by side on top of batter.
  3. Pour remaining batter over cookies.
  4. Bake at 350°F. for 45 minutes or until a toothpick inserted in the middle comes out clean. Let cool.

Peek-A-Boo St. Patrick's Day Cake

Prepare the buttercream frosting and add green food coloring. Mix thoroughly.

Peek-A-Boo St. Patrick's Day Cake

Frost the cooled cake and add sprinkles.

Peek-A-Boo St. Patrick's Day Cake

If you are having a party, wait for your guests to arrive before you cut the cake for the big reveal! They’ll be so surprised when they see the rainbow shamrock in the middle!

Peek-A-Boo St. Patrick's Day Cake

Peek-A-Boo St. Patrick’s Day Cake


  • For the Cake
  • 1 box of white cake mix (prepared according to package instructions)*
  • 1 box of chocolate cake mix (prepared according to package instructions)*
  • Food coloring of your choice (I used red, orange, yellow, green, blue)
  • Sprinkles
  • *Note - keep the cake batters in 2 separate bowls. One will be colored, the other stays white.
  • For the frosting -
  • 1 cup (2 sticks) unsalted butter, softened at room temperature
  • 3-4 cups powdered sugar
  • 1/4 cup heavy cream
  • 2 1/2 teaspoons vanilla extract (use clear vanilla flavoring for brighter color)
  • Green food coloring


  1. For the cake-
  2. Preheat oven to 350°F. Prepare the white cake mix according to the package instructions. Divide the batter into 5 bowls. Add the food coloring of your choice and mix well. I used red, orange, yellow, green and blue. Place the colored batter in gallon sized resealable plastic bags, cut a small corner and pipe the batter in rows onto a parchment lined 15"x18" half sheet pan or cookie sheet with raised edges. The rows should be touching. Then bake for about 8-10 minutes. Do not overbake. Let cool completely. Use a shamrock shaped cookie cutter to cut your cake into cookies.
  3. Grease and line a 10"x5" loaf pan with parchment paper, then prepare the batter from the chocolate cake mix. Pour a little in the bottom prepared pan. Line up your cookies, so that they are standing upright and right next to each other. They should be touching. Keep adding cookies until the pan is full of cookies from left to right. Pour the rest of the batter over the top of your colorful cookies. Bake for about 45 minutes or until a toothpick inserted in center comes out clean. Let cool. Frost the cake with buttercream frosting. Add sprinkles for more color and have fun cutting into this beauty!
  4. For the buttercream frosting
  5. Beat softened butter on medium speed with an electric or stand mixer. Beat for 3 minutes until smooth and creamy. Add powdered sugar, cream, and vanilla extract with the mixer running. Increase to high speed and beat for 3 minutes. Add more powdered sugar if frosting is too thin or more cream if mixture is too thick. Add green food coloring and mix completely.

Peek-a-boo St. Patrick's Day Cake

15 Responses to Peek-A-Boo St. Patrick’s Day Cake

  1. sara says:

    Loved Grandaddy’s St. Paddy’s day parties!! Always a fun time:) This shamrock cake would have fit right in!

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  10. Roxie Montague says:

    I’m going to attempt making your shamrock cake for a St. Patrick’s Day party. Since I won’t know how it turned out until I cut into it ( in front of all guests) I want to make sure I’m doing it correctly. Once inline all the shamrock cakes tightly across – what is stopping the chocolate batter from soaking into the shamrocks??? Thanks!

    • The shamrock cake pieces should fit together tightly in the pan, then the batter can’t get in. You could always do a trial run with solid colored shamrocks to make sure you can do it. Good luck!

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  12. Merrie Kay Gonyo says:

    Hi…I tried this for St Patrick’s Day in 2017. I printed ou the instructions and followed them exactly. I ran into some problems. First, the shamrock “cookies” did not rise as much as I think they should have. Any idea why?
    Secondly, the instructions said to “grease” the loaf pan but in re-reading and looking at your photos, I should have put parchment paper in the pan. My cake literally lost a side when removing it from the pan. Thirdly, because the shamrocks were thin, I stacked them on a cutting board and put the stack into the batter base. They would not stand upright so I was trying to hold them as well as add the rest of the cake mix. I needed up with a volcano cake that split into several pieces as I frosted it! We ate it anyway…my grandchildren loved it …got enough pieces with the shamrock for each of them! I’m not defeated and think this is a really cool idea but suggest some changes be made in instructions…especially the parchment paper lining. Thanks for the clever idea!

    • Hi Merrie, I’m sorry you ran into some problems with the cake. It can be a bit tricky making it. Practice makes perfect though. I’m so glad your grandchildren enjoyed it!

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