White-on-Rainbow Buttermilk Cake

This week's PPQ recipe comes from Beth of The Powdered Plum. The cake is actually called White-on-White Buttermilk Cake with Jack Daniel's Buttercream. However, as my nieces' 2-year birthday was around the corner and I was asked to make their birthday cake, I decided to use the Pastry Queen buttermilk cake as the base and added various shades of food coloring to construct the famous Whisk Kid Rainbow Cake. I've had this cake on my radar for awhile (thanks Steph!) but never really had a proper occasion to bake it, until now.

This cake was delicious - moist, crumbly and extremely flavorful from the buttermilk. Another winner from the Pastry Queen. I'm filing it away with some of my other favorite cake batters (Tuxedo Chocolate, Strawberry Chiffon and Coconut). The great thing about this cake is you can adapt and modify it to whatever you feel like, whether it's the batter, filling or frosting. You can add fresh strawberries and a whipped cream in between the layers to make fruit cake. You can add extracts to the batter, like strawberry or blueberry (which will be my next attempt) and make flavored cakes. I'm sure this batter will also bake up some yummy white cupcakes as well.

White-on-Rainbow Cake Batter
For the full cake recipe, head on over to Beth's blog for the ingredients and directions. This is a picture of the white cake batter.



I then separated out the dough into 6 bowls - you will end up with about 1 1/4 cup of batter per bowl. I used gel food coloring to color the batter - the colors are more concentrated and does not affect the overall taste of the cake.



The color of the batter stays pretty true to the color of the baked cake, albeit half a shade darker. I baked 3 layers at a time, at 350 degrees for about 10 minutes.



I ended up with 6 thin layers of brightly colored buttermilk cake. My oven didn't bake as even as I would have liked. According to the book, this batter is suppose to bake flat, eliminating the need to shave off any extra cake. My layers were still a bit lopsided - unfortunately they were so thin that you can't really shave off much without removing like half the cake.



I opted to use the buttercream from the Whisk Kid recipe- only because the Pastry Queen version seemed like it required an insane amount of butter (6 sticks!).

Buttercream Frosting
adapted from the Whisk Kid

Ingredients
9 egg whites
1 ¾ c (350 g) sugar
4 sticks (532 g) of butter, room temp
2 teaspoons vanilla extract

Directions
Cook the egg whites and sugar in a small saucepan over medium heat, whisking constantly, until the sugar is completely dissolved (test by rubbing some between your fingers. If it's completely smooth, it's done). Pour into another bowl (a stand mixer is preferable) and whip on high speed until room temp. Then, on a medium-slow speed, add the butter, waiting until each piece is completely incorporated before adding the next. After all the butter has been added, turn the mixer back to high speed and whip until it has come together, about five minutes. Add the extract, beat briefly and then use.
If the buttercream seems soupy after all of the butter is added and does not come together after whipping, refrigerate for 5 to 7 minutes and continue whipping until it becomes fluffy and workable.

Cake Assembly
There is no real rule for the layering - you can start and end with any color. I opted to follow the recipe and started with purple on the bottom and ending with red at the top.





In the Whisk Kid's version of the cake, she made two batches of this buttercream. One to fill and crumb, the other to frost. The result is a very pretty cake with defined layers of color due to the thick white frosting applied between each layer. I am not a fan of buttercream so I opted to frost the cake sparingly - the result is a shorter cake with cake layers that blend into each other rather than separated out.



This cake was delicious and an impressive sight once you cut into it. It was my trial run - for the actual birthday, I may stick with the pink and purple theme of the party and do 6 different shades of those two colors - and adding strawberry and blueberry extracts to the batter for added flavor.

Thanks Pastry Queen and the Whisk Kid for such a creative and yummy cake!