Hidden Design Cake: Chocolate Rainbow Cookie Heart

Hidden Design Cake: Chocolate Rainbow Cookie Heart

Great British Bake Off/Baking Show, Series 3 (UK) 

Episode 1:

Showstopper Challenge– Hidden Design Cake

My first showstopper challenge was definitely a challenge for me! I decided to try and make a chocolate cake with a hidden rainbow cookie heart design inside. There are plenty of things I would do differently next time, but I am definitely very happy with the rainbow heart I saw when I cut into the cake. All that work was worth it!  

I decided on this particular cake because I wanted to use the rainbow cookie recipe my grandma just sent me and what would go better with rainbow cookies than chocolate?  

This cake took me a couple of days to complete. The main reason for this was the rainbow cookies because the three layers of cookie (separated by jam) have to be weighed down overnight in the refrigerator. I used a giant book!

rainbow cookies

On the second day, after I came home from work I baked the chocolate cake and made the frosting which were simple enough.  I always use the same recipe from Add a Pinch because it always comes out so moist and delicious. There’s a reason she calls it the best chocolate ever. Because it is. I user her chocolate frosting recipe as well.

Then came the fun part: assembling and decorating! The assembling involved cutting out two rectangles for the cake, cutting the rainbow cookie into what resembled a really long heart and putting cake back wherever there were holes. Pictured above, is the process about halfway done. 

One thing I learned from this challenge is that I should have used icing more to combine all the crumbly bits of cake I used as filler for the holes. After cutting into the finished cake slice, it felt apart a bit because I didn’t use icing. Lesson learned!

chocolate cake

Here’s the super delicious rainbow cookie recipe. They definitely do not need to be surrounded by chocolate cake to be delicious. 

rainbow cookies

Grandma's Rainbow Cookies

Sweet Melissa
Deliciously addicting traditional Italian cookie.
Prep Time 45 mins
Cook Time 13 mins
Compressing Time 8 hrs
Total Time 9 hrs
Course Dessert, Snack
Cuisine American, Italian


  • 1 Tube Almond Paste
  • 3 Sticks Dairy Free Butter, cubed
  • 4 Eggs, Separated
  • 1 Tsp Vanilla Extract
  • 1 Tbsp Almond Extract
  • 2 Cups All-Purpose Flour
  • ¾ Cup Granulated Sugar
  • 10 Drops Green Food Coloring
  • 8 Drops Red Food Coloring
  • 1 Jar Seedless Raspberry Jam
  • 1 Package Semi-Sweet Chocolate


  • In a food processor, break up almond paste, butter, sugar, egg yolks, and almond extract. Beat 5 minutes or until smooth. Place into a large bowl, stir in flour with whisk. Set aside.
  • In a dry glass bowl, whip egg whites and vanilla until stiff peaks form. Fold egg whites into almond mixture until incorporated. Do not overmix!
  • Get two more bowls and divide batter into three equal parts. Add green food coloring to one bowl, red food coloring to another, and leave the last alone. Gently mix in the coloring.
  • Preheat oven to 350°F. Line 3 9x13x2" tins with parchment paper. Spread batter into pans. Bake 13-14 minutes. Let cool 10 minutes.
  • Spread jam on the green layer, place the white cake on top and then spread jam on the white layer and place the red layer on top. Leave the stacked cakes in the first pan, cover with wax paper, then aluminum foil, and put in the refrigerator with something heavy on top to press down (like a large book).
  • The next day, melt the chocolate and spread over top of cake. Let cool, then cut into rectangles the size of your choosing. Keep refrigerated and enjoy!
Keyword Cookies, Dairy-Free

Here’s the delicious chocolate cake recipe. If you’re a chocolate lover, you will be forever addicted to this cake. I have a dairy allergy, so I adapted the recipe from Add a Pinch blog to be dairy free.  

chocolate cake

Classic Chocolate Cake (Dairy-Free)

Sweet Melissa, Recipe from Add a Pinch Blog with Dairy-Free Substitutions
Amazingly moist and super chocolatey.
Prep Time 20 mins
Cook Time 30 mins
Course Dessert
Cuisine American
Servings 10 People


  • 2 9-Inch Cake Tins



  • 2 Cups All-Purpose Flour
  • 2 Cups Granulated Sugar
  • ¾ Cup Cocoa Powder
  • 2 Tsp Baking Powder
  • 1 ½ Tsp Baking Soda
  • 1 Tsp Salt
  • 1 Cup Coconut Milk
  • ½ Cup Avocado Oil
  • 2 Eggs
  • 2 Tsp Vanilla Extract
  • 1 Cup Boiling Water


  • 1 ½ Cups (3 Sticks) Dairy-Free Butter
  • 1 Cup Cocoa Powder, sifted
  • 5 Cups Powdered Sugar
  • ½ Cup Coconut Milk
  • 2 Tsp Vanilla Extract


  • Preheat oven to 350°F. Grease and flour two 9-inch cake pans.
  • Add the flour, sugar, cocoa, baking powder, baking soda, and salt to a large bowl or stand mixer. Whisk until combined.
  • Heat water to a boil on the stove.
  • Add the milk, oil, eggs, and vanilla to the dry ingredients. Beat until combined. Then slowly pour in boiling water while mixing.
  • Distribute batter into cake pans. Bake 30-35 minutes or until a toothpick comes out clean. Let cool.
  • Gather the frosting ingredients. Beat the butter until fluffy and then add in the milk and vanilla. Beat in the sugar a cup at a time and add in the cocoa powder. Beat until it's smooth and all incorporated.
  • Assemble our cake! Put a layer of frosting on the first cake, place the next cake on top and cover the whole cake in frosting. Enjoy!
Keyword Dairy-Free

Learn more about my great baking challenge. Or you could try this yummy Apple Pear Tarte Tatin.

Never miss a post! Sign up for my monthly newsletter:

This Post Has 2 Comments

Leave a Reply

Recipe Rating