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Ube Layer Cake

yield: 4 8-inch layers
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Special Equipment

  • Special Equipment: a handheld electric mixer with whisk and mixing attachments (see baker's notes)
  • a candy thermometer (preferably digital)
  • tweezers

Ingredients

For the Ube Layer Cake

  • 3 cups (12 ounces) cake flour
  • 3 teaspoons baking powder
  • 1 teaspoon kosher salt
  • 5 large eggs, divided into 5 whites and 5 yolks
  • 2 1/4 cups 15.75 ounces granulated sugar, divided into 1/4 cup (1.75 ounces) and 2 cup (14 ounces) portions
  • 6 tablespoons 5 ounces unsalted butter, at room temperature
  • 1 cup 8 ounces ube halaya jam (see baker's notes for sources)
  • 1 tablespoon ube extract (see baker's notes for sources)
  • 2 teaspoons purple food coloring
  • 1 1/4 cups (10 ounces) whole milk, at room temperature

For the Vanilla Swiss Meringue Buttercream Frosting

  • makes around 4 1/2 cups, enough for one layer cake
  • 1/2 cup plus 2 tablespoons 5 ounces large egg whites (from about 5 large eggs)
  • 1 1/4 cups 8.75 ounces granulated sugar
  • 2 cups 16 ounces unsalted butter, at room temperature and cut into 1-inch cubes
  • 2 teaspoons pure vanilla extract

For the Ube Swiss Meringue Buttercream Frosting

    makes around 3 1/4 cups, enough for one layer cake

    • 1/2 cup (4 ounces) large egg whites (from about 4 large eggs)
    • 1 cup (7 ounces) granulated sugar
    • 1 1/2 cups (12 ounces) unsalted butter, at room temperature and cut into 1-inch cubes
    • 2 teaspoons ube extract (see baker's notes for sources)
    • 2 teaspoons purple food coloring
    • 1/4 cup (2 ounces) ube halaya jam (see baker's notes for sources)

    Assembly

    • three or four sheets edible gold leaf (see baker's notes for sources)

    Instructions

    For the Ube Layer Cake

    • Center a rack in the oven and preheat to 350 (F). Prepare four 8-inch cake pans by spraying generously with cooking spray. Line the bottom of each cake pan with a parchment paper circle and spray with cooking spray as well. Set pans aside.
    • In a medium bowl, combine 3 cups cake flour, 3 teaspoons baking powder, and 1 teaspoon kosher salt. Whisk to combine and set aside.
    • Place 5 large egg whites in a large bowl and use a handheld electric hand mixer to whisk on medium speed until the egg whites are frothy. Raise the mixer speed to high and gradually beat in 1/4 cup granulated sugar. Continue whisking until the egg whites form stiff peaks. Set aside.
    • In the bowl of a freestanding electric mixer fitted with a paddle attachment, combine the remaining 2 cups granulated sugar and 6 tablespoons unsalted butter. Beat on medium speed until light and fluffy, about 3 to 5 minutes. Lower the mixer speed to its slowest setting and add 5 large egg yolks, one at a time, only adding the next egg yolk when the previous one is fully incorporated. Once all the egg yolks have been added, add 1 cup ube halaya jam, 1 tablespoon ube extract, and 2 teaspoons purple food coloring. Continue beating until combined and the mixture is a homogenous bright purple, using a rubber spatula to scrape down the paddle and the sides and bottom of the bowl as needed.
    • With the mixer on low speed, add the dry ingredients (from the 2nd step) in three parts, alternating with 1 1/4 cups whole milk in two parts, beginning and ending with the dry ingredients. Mix on low speed just until the ingredients are combined.
    • Once the ingredients are combined, remove the bowl from the mixer and fold in one-fourth of the beaten egg whites (from the 3rd step) to lighten the batter. Once incorporated, fold in the rest of the egg whites until no steaks remain — be careful not to fold or mix too much, or the batter will deflate and you'll end up with flat and dense cakes. Fold only until the whites disappear into the batter. The batter should lighten and look almost like a purple mousse.
    • Divide the batter into the 4 prepared cake pans and transfer to the preheated oven. Bake for 30 to 35 minutes, or until a skewer inserted into the center of each cake comes out clean and the top of each cake bounces back when gently poked. Transfer to a wire rack to cool completely before decorating.

    For the Vanilla Swiss Meringue Buttercream Frosting

    • Place 1/2 cup plus 2 tablespoons large egg whites and 1 1/4 cups granulated sugar in a medium heatproof glass bowl. Use a rubber spatula to mix the ingredients together until combined, scraping down the sides of the bowl. Place the glass bowl on top of a medium sauce pan filled with an inch or two of water, ensuring that the bottom of the glass bowl does not touch the water. Cook over medium-high heat, mixing the egg whites and sugar occasionally and scraping down the sides of the bowl, until it registers 160 (F) on a candy thermometer. This will take around 10 to 15 minutes, depending on how aggressive you are with your heat.
    • Once the mixture is 160 (F), carefully pour the mixture into the bowl of a freestanding electric mixer fitted with a whisk attachment. Whisk the mixture on high speed for 8 to 10 minutes, until it holds medium-stiff peaks and the outside of the mixer bowl is at room temperature. Stop the mixer and use a rubber spatula to scrape down the whisk and bottom and sides of the bowl. Replace the whisk attachment with the mixer's paddle attachment.
    • With the mixer on low speed, gradually add 2 cups cubed unsalted butter, one or two cubes at a time. Once all the butter is incorporated, add 2 teaspoons pure vanilla extract. Mix on low speed for a few more seconds until incorporated, and then turn the mixer speed up to medium-high and beat until the buttercream is silky smooth, 3 to 5 minutes.

    For the Ube Meringue Buttercream Frosting

    • Place 1/2 cup large egg whites and 1 cup granulated sugar in a medium heatproof glass bowl. Use a rubber spatula to mix the ingredients together until combined, scraping down the sides of the bowl. Place the glass bowl on top of a medium sauce pan filled with an inch or two of water, ensuring that the bottom of the glass bowl does not touch the water. Cook over medium-high heat, mixing the egg whites and sugar occasionally and scraping down the sides of the bowl, until it registers 160 (F) on a candy thermometer. This will take around 10 to 15 minutes, depending on how aggressive you are with your heat.
    • Once the mixture is 160 (F), carefully pour the mixture into the bowl of a freestanding electric mixer fitted with a whisk attachment. Whisk the mixture on high speed for 8 to 10 minutes, until it holds medium-stiff peaks and the outside of the mixer bowl is at room temperature. Stop the mixer and use a rubber spatula to scrape down the whisk and bottom and sides of the bowl. Replace the whisk attachment with the mixer's paddle attachment.
    • With the mixer on low speed, gradually add 1 1/2 cups cubed unsalted butter, one or two cubes at a time. Once all the butter is incorporated, add 2 teaspoons ube extract and 2 teaspoons purple food coloring. Mix on low speed for a few more seconds until incorporated, and then turn the mixer speed up to medium-high and beat until the buttercream is silky smooth, 3 to 5 minutes. Lower the mixer speed to its slowest setting and gradually add 1/4 cup ube halaya jam until combined.

    Assembly

    • Once the layer cakes have cooled completely, use the Vanilla Swiss Meringue Buttercream Frosting to assemble the cake. Use around 2/3 cup of frosting between each cake layer, and use the remainder of the vanilla buttercream to cover the cake completely with a smooth layer of frosting (see baker's notes for resources). Transfer to the refrigerator to chill for at least 1 hour and allow the buttercream to set.
    • Once the vanilla buttercream has set, remove from the refrigerator. Cover the top half of the cake with Ube Swiss Meringue Buttercream Frosting. Don't worry about making it an even half — you actually want the ube border to be uneven around the cake for a more interesting kintsugi design. Use an offset spatula to smooth the ube frosting completely.
    • Use tweezers to carefully apply a small tear of gold leaf at the border where the ube buttercream and vanilla buttercream meet. As you place the gold leaf on the cake, the gold leaf will wrinkle to give the cake the kintsugi effect. Continue tracing the border of the two buttercreams with gold leaf until complete. For a video of the process, be sure to check out my Instagram Stories!