Naturally Blue Birthday Cake

Last weekend, we celebrated my parents' birthdays. It's funny that their birthdays are two years and five days apart; Jake and I are two years and seven days apart. So, joint parties are the norm. In any case, it's taken me a week to get this written up.

I had just gotten some blue butterfly pea flower powder, erroneously named blue matcha, and wondered if the color would bake out. When it stayed blue, on a test run, I decided to make a naturally blue birthday cake of Nonno and Nonna. You can read a little bit about "blue matcha" in my Magical Blue Moon Matcha Cocktail post.

Ingredients makes one 9" layer

(I made four layers - two blue and two plain)

Cake

• 2 C flour
• 1 t baking powder
• 1 t salt
• 1/4 t baking soda
• 1 C whole milk plain yogurt
• 1-1/4 C cane sugar
• 3/4 C olive oil
• 2 large eggs
• 1 t organic vanilla paste or extract 
• Also needed: butter for greasing pans, parchment paper, 9" cake pan
• For the blue layers: 1 T blue butterfly pea flower powder*

Buttercream

• 5 large egg yolks
• 1/3 C water
• 1 C organic granulated sugar
• 1 T organic corn syrup
• 2 C butter, softened
• 1 T organic vanilla paste (prefer Taylor & Colledge)
• 2 T + 1 t blue butterfly pea flower powder

To Assemble

• caramel or dulce de leche (storebought or homemade)

Procedure

Cake
Preheat oven to 350 degrees F. Butter a 9" round cake pan and line the bottom with parchment paper. Set aside.

Whisk together all of the dry ingredients in a medium mixing bowl. Whisk together the yogurt, sugar, and olive oil until well-combined. Add the eggs to the olive oil mixture, one at a time, whisking very well after each, then stir in the vanilla extract. 

Add the dry ingredients and yogurt mixture to the olive oil mixture and whisk until well-combined. If making the blue layer(s), whisk in blue butterfly pea flower powder.

 Pour the batter into the prepared pan and bake until a toothpick inserted in the center comes out clean, approximately 40 to 45 minutes. 

Let cool on a wire rack before inverting. Let cool completely before assembling the cake. Make the buttercream.

Buttercream

Place egg yolks in a mixing bowl and beat on high until they are thick, pale, and ribbon off the whisks.

Combine water, sugar, and corn syrup in a small saucepan. You can attach a candy thermometer to the side; I just kept testing until it reached soft-ball stage. If you're using a thermometer, heat until it reaches 238 degrees F. For testing otherwise, dip a spoon into the syrup, then into ice cold water. The syrup should immediately set up into a soft ball. Mine took about 8 minutes to reach the correct consistency.

Once the syrup is ready, remove it from the heat. While one hand hold the mixer, use the other hand to pour the syrup into the yolks. When all of the syrup is added, turn the mixer up to high and beat until the yolks have doubled in size and have reached medium peak stage. The bowl should be cooled and just lukewarm to the touch. Mine took about 9 minutes.

Begin adding butter, one tablespoon at a time, mixing well after each addition. The more butter you add, the more firm the buttercream will be. Once your buttercream resembles what you think of as buttercream, add in the vanilla paste. If making a few natural decorations, remove a few tablespoons of buttercream before adding in 2 T blue butterfly pea flower powder. Beat until well-combined and evenly colored.

Once the cake layers have cooled completely, use a serrated knife to cut the layers flat.

Spread a generous layer of softened caramel between the layers and place them on your serving platter.

Smooth the buttercream over the top and along the sides.

Pipe on the natural colored decorations. Then, add the remaining 1 t blue butterfly pea flower powder to make a deeper blue. Add those buttercream details to the cake. Refrigerate to let the buttercream harden.

Top with candles and make sure your guests know the rule: if you don't sing, you don't get cake!

*This blog currently has a partnership with Amazon.com in their affiliate program, which gives me a small percentage of sales if you buy a product through a link on my blog. It doesn't cost you anything more. If you are uncomfortable with this, feel free to go directly to Amazon.com and search for the item of your choice.