Butterfly Pea Cake with Lemon Cream Cheese Frosting

Blue is a very tricky color to achieve in cakes regardless of whether you tint it with naturally derived blue powders (like the butterfly pea flowers) or store bought blue coloring. 

Any slightest tinge of yellow in any of the cake ingredients (like butter or egg yolks which are typically used in most cakes including vanilla cake and pound cake) will turn the blue cake batter into green or teal. 

To preserve the pure blue color of the butterfly pea flowers, this blue cake batter is made without any egg yolks or butter. Egg yolks are totally eliminated while butter is replaced with shortening.

The resulting cake has a lovely pastel blue interior and makes an even prettier cake with a white cream cheese frosting.

❓What is butterfly pea flower?

• Butterfly pea plant is native to the Southeast Asia region. It produces blue edible flowers that are widely used in the Southeast Asian cuisine, both for its beautiful color as well as its medicinal properties. 
• Also known as Asian Pigeonwings or blue pea flowers, the butterfly pea flowers are blue in color. The rich color is often extracted (by steeping the flowers in hot water) and used as a natural dye in food (like the butterfly pea cookies and butterfly pea jelly) and drinks (like this butterfly pea drink, butterfly pea latte, butterfly pea lemonade and butterfly pea milk tea). 
• The flowers can be used in fresh form, or in dried or powder form. While it may be difficult to readily obtain the fresh flowers, you can find the dried butterfly pea flowers in online stores or grocery stores selling South East Asia food items.
• The powder form of the blue butterfly pea powder is also known as blue matcha powder. 

• Egg whites - use fresh eggs and make sure they are at room temperature. 
• Granulated sugar (caster sugar) - use white sugar to preserve the white base for the cake.
• Shortening - helps keep the batter completely white to preserve the blue color of the butterfly pea. Butter will cause the cake to become a teal colored instead of blue.
• Self raising flour + cornstarch + salt - Cornstarch helps with the soft and delicate texture of the cake. Make sure to sift both flours (with salt) before using to break any lumps and to aerate the flour.
• Vanilla extract - flavoring is important for this cake as shortening is quite tasteless.
• Blue butterfly pea flower powder (Blue matcha powder) - contributes to the natural blue color of the cake. It is best to purchase the flowers in powder form than making at home with dried flowers as the powder has to be fine like flour.

• Cream cheese - use full fat cream cheese that is sold in blocks. Spreadable cream cheese will not work for this recipe as it will be too soft.
• Powdered sugar (icing sugar) - sift first to break any lumps as powdered sugar tends to be lumpy.
• Shortening - Helps to stabilize the cream cheese especially in warm climates. It also helps maintain the white color of the frosting.
• Lemon zest & juice - adds a lovely flavor to the cream cheese frosting.

Decoration (Optional)

• Fondant flowers - These are cut using fondant flower cutters in 2 different sizes and 2 different shades of blue. You can make your own fondant with my marshmallow fondant or homemade fondant recipe or store bought fondant.
• Fresh berries (blueberries) - I used blueberries to match the color of the cake.

Step 1: Melt the shortening. Use low heat and turn the heat off as soon as the shortening is almost all melted. The rest will continue to melt in the heat. Set it aside to cool (image 1).

Step 2: Separate the egg whites and egg yolks. The egg yolks as they are not required in this recipe. Add the egg whites into an absolutely grease-free bowl (image 2).

Step 3: Whisk the egg whites and add half of the sugar. Start by whisking just the egg whites. Use medium speed. Whisk until they turn frothy and increase in volume.

Test by turning off the mixer and lifting the beaters. If you see stiff peaks formed on the beaters (like in image 3), you can start adding half of the granulated sugar.

Note: Sprinkle the sugar gradually while whisking instead of dumping it all at once to avoid the eggs from deflating.

Step 4: Continue to whisk on medium speed until the egg whites turn glossy and stiff peaks form again (image 4). Set aside.

Step 5: Measure the dry ingredients. Add self raising flour, cornstarch, salt and the butterfly pea powder into a bowl (image 5). Sift twice to combine the ingredients and aerate the flour (image 6).

Step 6: Mix in the remaining half of the granulated sugar. Stir with a hand whisk until well combined (images 7 & 8).

Step 7: Combine wet ingredients into the dry ingredients. Make a well in the center of the sifted dry ingredients.

Note: The best way to mix the liquids into the flour mixture (to avoid the flour from lumping) is to make a well in the center and pour the liquids in.

Pour in the melted shortening, followed by the milk and the vanilla extract (image 9).

Mix with a hand whisk until the mixture turns smooth and there are no lumps (image 10).

Note: Start mixing in the center in circular motion and pull in the flour mixture into the center with the whisk as you mix.

Step 8: Fold in the egg whites. Scoop one third of the whipped egg whites into the flour mixture and fold it in gently.

Scrape the sides and bottom of the bowl as you fold. Continue with another one third of the whipped egg whites. Fold well (images 11 & 12).

Finally, pour the blue batter into the remaining whipped egg whites. Fold gently and well, until there are no streaks of the whipped egg whites left (image 13).

Note: Transferring the batter into the egg whites bowl will ensure there is no flour mixture left unmixed at the bottom of the bowl. But do not overmix the batter to avoid the egg whites from deflating.

Step 9: Pour the batter into cake tins. Divide between two well greased 7 inches round cake tins.

Make sure to line the bottom of the tins with parchment paper. This is crucial as the cake tends to stick to the bottom of the pan even after greasing (image 14).

Note: To ensure the batter is equally divided between the tins, you may want to weigh the cake tins with the batter in it. This will help ensure the cakes bake evenly and with same height.

Step 10: Bake the cakes for 45 minutes in the preheated oven at 175℃ until the top is soft but firm to the touch.

Make sure the cakes are well baked or they risk collapsing once you remove from the oven. Remove the cakes from the oven and let them cool in the tins for about 3 to 4 minutes.

Use a butter knife or palette knife to loosen the sides of the cake from the tin.

Turn the cakes over onto wire racks and peel off the parchment paper lining. Turn the cakes over again so that they face upwards. Let them cool down completely before frosting.

Note: Keep the cakes covered with a kitchen towel as they are cooling down to prevent them from becoming dry.  It also helps to wrap them in plastic wrap while they are still warm and refrigerating until they cool down completely to lock the moisture.

Step 11: Make the cream cheese frosting. Measure cream cheese into a medium bowl. Add the shortening. Cream both until smooth and creamy (image 15). 

Next, sift in the powdered sugar. You can either sift it directly into the creamed mixture or sift it separately and then add it into the bowl (image 16).

Mix the sugar into the creamed cheese with a spatula first to avoid the sugar from flying all over as you turn on your mixer (image 17).

Once the sugar is lightly moistened, whip the frosting until it turns smooth (image 18). Add the lemon zest and lemon juice and beat again until well combined.

Step 12: Fill and cover the cake with the frosting. To prevent the brown crust around the cake layers from showing, use a sharp knife or a serrated knife to slice it off from the top, bottom and sides of each cake layer (image 19).

Place the first cake layer on a cake plate. Spoon some cream cheese frosting onto the cake layer and spread it with a palette knife (image 20).

Note: Use a turntable for easy frosting of the cake.

Top with the second cake layer. Start by covering the top with frosting before doing the sides (images 21 & 22). Level the frosting (but it need not be super smooth as you will be doing designs on it with the palette knife (see the steps below).

Note: To avoid the cake crumbs from getting mixed into the frosting, you can give the cake a thin layer of crumb coat like in this Earl Grey lavender cake. Refrigerate for a few minutes to allow the frosting to firm up and then apply the final layer of frosting.

Step 13: Decorate the cake. Hold the palette knife at about 45 degrees angle on top of the cake, in the center.

Apply very light pressure on the frosting and move the knife outwards as you turn the turntable with the other hand. This will create a pretty circular pattern on the cake (image 23). 

For the sides, use the same palette knife (wipe off any excess icing that is stuck to it), and move the knife from bottom to top, creating slanting lines on the side (image 24). 

To complete the decoration, roll some fondant thin and cut out the flowers using small flower cutters (image 25). 

Arrange the flowers on the cake, combined with fresh blueberries to create a pretty pattern on it (image 26).

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