Purple Velvet Cake with Cream Cheese Frosting {Gonzo Cake} from Baked Occasions
Gonzo Cake from the book Baked Occasions. Moist purple velvet cake filled and frosted with classic cream cheese frosting and topped with a medley of sprinkles.
Ingredients
For the Purple Velvet Cake:
  • 1 4-ounce/115 g package purple yam powder (about 1/2 cup plus 2 tablespoons; see Note)
  • 1/4 cup 60 ml canola oil or other vegetable oil
  • 2 1/4 cups 285 g cake flour
  • 3/4 cup 90 g all-purpose flour
  • 1 tablespoon baking powder
  • 1 teaspoon baking soda
  • 3/4 teaspoon kosher salt
  • 4 ounces 1 stick/115 g unsalted butter, softened, plus more for the pans
  • 1/4 cup 50 g vegetable shortening, at room temperature
  • 2 cups 400 g granulated sugar
  • 1 tablespoon pure vanilla extract
  • Blue and red food dyes or gels
  • 4 large egg whites at room temperature
For the Cream Cheese Frosting:
  • 3 cups 340 g confectioners' sugar
  • 8 ounces 2 sticks/225 g unsalted butter, softened
  • 2 8-ounce/226-g packages cream cheese, softened
  • 1 tablespoon plus 1 teaspoon pure vanilla extract optional
  • 1/2 teaspoon kosher salt
Instructions
Make the Purple Velvet Cake:
  1. Preheat the oven to 325˚F (165˚C). Butter three 8-inch (20-cm) cake pans, line them with parchment paper, and butter the parchment. Dust with flour and knock out the excess.
  2. In a small saucepan over very low heat, stir together 2 cups (480 ml) of water with the purple yam powder and cook, stirring occasionally, until the mixture is rehydrated, between 5 and 20 minute depending on the heat. Once the mixture looks and feels like mashed potatoes (or mashed yams) remove it from the heat and whisk in the canola oil.
  3. In a large bowl, sift both flours, the baking powder, baking soda, and salt. Set aside.
  4. In the bowl of a standing mixer fitted with the paddle attachment, beat the butter and shortening on medium speed until cream, 3 to 4 minutes. Add the sugar and vanilla and beat on medium speed until the mixture is light and fluffy, about 3 minutes. Turn the mixer to low. Add the flour mixture in three equal parts, alternating with the purple yam mixture, beginning and ending with the flour mixture. Scrape down the sides of the bowl with a rubber spatula and then mix on low speed for a few more seconds.
  5. Mix equal drops of red and blue food dyes in a small bowl to make purple, then scrape it into the cake batter and mix until a pale purple color is achieved.
  6. In a clean bowl, whisk the egg whites by hand or in your standing mixer until soft peaks form, do not overbeat. Using a rubber spatula, gently fold the egg whites into the batter.
  7. Divide the batter equally among all three pans. Use your spatula to spread the batter evenly. Bake the cakes, rotating the pans halfway through baking, until a toothpick inserted in the center of the cakes comes out clean, 20 to 30 minutes. Transfer the pans to a wire rack and cool for 20 minutes. Invert the cakes onto the rack, remove the pans, and let them cool completely. Remove the parchment.
Make the Cream Cheese Frosting:
  1. Sift the confectioners' sugar into a large bowl and set aside.
  2. In the bowl of a standing mixer fitted with the paddle attachment, beat the butter until it is completely smooth. Add the cream cheese and beat until combined.
  3. Add the confectioners' sugar, vanilla, if using, and salt and beat just until smooth; do not overbeat or the frosting will lose structure. Chill the frosting in the refrigerator for about 5 minutes. (The frosting can be made up to 24 hours ahead; cover the bowl tightly, refrigerate, and let the filling soften at room temperature before using.)
Assemble the Gonzo Cake:
  1. Place one cake layer on a serving platter. Trim the top to create a flat surface and even spread about 1 1/4 cups (330 g) of the frosting on top. Add the next layer, trim and frost it, then add the third layer. Trim the top layer. Spread a very thin layer of frosting over the sides and top of the cake (a crumb coat, which helps to keep loose cake crumbs under control when you frost the outside of the cake) and place it in the refrigerator to firm up, about 15 minutes.
  2. Remove the cake from the refrigerator. Frost the sides and top with the remaining frosting. Sprinkle the outer edge of the top of the cake with the sprinkles, if you like. Chill the cake in the refrigerator to set the frosting, about 15 minutes. Slice and serve.
How to Store:
  1. This cake can be covered in a cake saver in a cool room for up to 3 days. If you refrigerate it, make sure to cover it tightly and bring it back to room temperature before serving.