The clever girl is 6 years old! It is hard to believe. I made her a Rainbow Cake for her birthday, as a total surprise. She had asked for a chocolate cake, and since I couldn't do a chocolate rainbow cake, I used chocolate buttercream frosting for the outside of the cake. I also made some homemade chocolate ice cream, which you will see on a separate post. (It was DELICIOUS, so make sure to check back for that recipe!!)
"How'd you DO that???"
Indeed. It actually isn't hard, it is just more time consuming than making a solid colored cake, as every layer cooks separately. And since I only have two 8-inch cake pans, it took a while to get all of the layers baked. The key is to start out with a great "white" cake recipe. I used a recipe from Cooks Illustrated, which I had never used before, and will now probably become my go-to white cake recipe. I think finding a good white cake recipe can be hard, but this one really hit it right. It is delicious!
White Layer Cake
adapted from Cooks Illustrated
alterations for Rainbow Cake in italics
makes 1 double-layer 9-inch cake (6-layer 8-inch rainbow cake)
2 1/4 cups cake flour, plus more for dusting pans
1 cup whole milk, at room temperature
6 large egg whites, at room temperature
2 teaspoons almond extract
1 teaspoon vanilla extract
1 3/4 cups granulated sugar
4 teaspoons baking powder
1 teaspoon salt
12 tablespoons unsalted butter, softened but still cool
Red, orange, yellow, green, blue and purple GEL food color. (Liquid color will not be vibrant enough and could change the structure of the batter - too much added liquid)
Set oven rack in the center, and heat to 350F. Butter two 9-inch round cake pans (8-inch round cake pans), line bottoms with parchment, butter parchment, and dust with flour. (Weigh your empty mixing bowl).
Pour milk, egg whites, and extracts into a 2-cup glass measure and whisk until blended. In the bowl of an electric mixer, mix the cake flour, sugar, baking powder and salt at low speed. Add the butter and continue to beat until the mixture resembles moist crumbs. There should be no powdery streaks.
Add all but 1/2 cup of the milk mixture to the crumbs and beat at medium speed for 1 1/2 minutes. Add the remaining 1/2 cup of the milk mixture and beat for 30 seconds more. Stop mixer and scrape the bowl. Return the mixer to medium speed and mix for 20 seconds.
Divide the batter evenly between the two prepared cake pans. (Weigh the full mixing bowl and subtract the weight of the empty bowl. This is the weight of the batter. Divide that number by 6 and this is the amount of batter you will put into 6 separate bowls. Gently whisk several drops of gel color into each bowl. The color of the cake will be the same as the color of the unbaked batter, so mix in enough color to get the vibrancy that you want. Pour two of the colors into the prepared 8-inch pans. If you have more than two 8-inch pans, lucky you! Do more! However for baking purposes, you should still bake only two at a time. If you need to re-use the pans, make sure you wipe them out each time, and run cool water over the outside bottom of the pan so that the pan is no longer hot before you re-butter, re-parchment, re-butter, and re-flour the pans.) Use a rubber spatula to spread the batter to the pan walls and smooth the top. Place the pans into the oven, at least 3 inches apart and 3 inches from the oven walls. Bake until a cake tester inserted in the center comes out clean, about 23-25 minutes (12-13 minutes).
Let the cakes rest in the pans for 3 minutes. Invert onto wire racks, remove the parchment, and then re-invert onto a different wire rack. Allow to cool completely. (Do not worry if your rainbow layers are really thin, almost like pancakes. Once you stack them up with layers of cream or frosting in-between, you will have a very tall cake.)
For the layers in my cake, I used a stabilized whipped cream. You can use whatever you want. I thought that white in-between the rainbow layers would accent the colors nicely, and would be a tasty filling! If you choose to use frosting, you'll probably need to double your frosting recipe to have enough. There are several methods to stabilize whipped cream. I found one using non-fat dry milk and decided to try that. You can also use unflavored gelatin or cream cheese. For this cake, I used 2 1/2 cups of whipped cream, less powdered sugar, and a mix of vanilla and almond extracts, as I like that flavor combination!
Stabilized Whipped Cream
1 cup heavy whipping cream
1 TB non-fat dry milk
~1 teaspoon vanilla extract
~2 TB to 1/4 cup sifted powdered sugar, to taste
Whip the heavy whipping cream and nonfat dry milk to a soft peak stage, then add the vanilla and powdered sugar (to taste). Whip to desired consistency. Whipped cream can be dolloped, piped, layered, and will keep its consistency for at least 24 hours, probably more!
Days later, the clever girl is still talking about her rainbow cake! Success!