Filipino Purple Yam Chiffon Cake From Scratch
For the Chiffon Cake:
2 1/4 cups cake flour [254 g]
3 teaspoons baking powder [12 g]
1/2 cup granulated sugar [100 g]
1 teaspoon salt [6 g]
8 egg yolks (egg whites will be used for meringue mixture) [160 g]
1/2 cup canola (or vegetable) oil [120 mL]
3/4 cup whole milk [180 mL]
1/2 cup ube halaya (ube jam) [120 mL]
1 tablespoon ube extract [15 mL]
1 teaspoon purple food coloring (gel paste) [5 mL]
8 egg whites [240 g]
1 teaspoon cream of tartar [3.4 g]
3/4 cup granulated sugar [150 g]
For the Frosting:
8 oz cream cheese (at room temperature) [226 g]
2 cups heavy cream [474 mL]
1/2 cup granulated sugar [100 g]
1 teaspoon vanilla extract [5 mL]
Ube Chiffon Cake:
Preheat the oven to 340 F (170 C). Prepare two 9" round, 2 1/2" high pans by lining bottoms with parchment paper. Do not grease the parchment paper or the sides of the pans. Line the outer sides of the pans with cake strips soaked in cold water to avoid doming.
In a large bowl, sift together 2 1/2 cups of cake flour, 3 tsp baking powder, 1/2 cup of granulated sugar, and 1 tsp table salt. Then add in 8 egg yolks, 1/2 cup vegetable oil, 3/4 cup milk, 1/2 cup ube halaya, 1 tbsp ube extract, and 1 tsp of purple food coloring (gel paste). Beat this with an electric mixer or by hand just until smooth and well blended.
In a separate bowl, beat 8 room temperature egg whites and 1 tsp cream of tartar on high speed until frothy. Very slowly add in 3/4 cup sugar and beat until stiff peaks are formed. Gradually and gently fold in the beaten egg whites into the cake mixture until very well combined. Divide the batter equally into the two prepared pans.
Bake in the preheated oven at 340 F (170 C) for about 35-45 minutes or until a toothpick inserted into the center of the cake comes out clean. Invert pans into wire rack immediately and cool completely (while still in the pan).
Once they're cool, it should be easy to lift off the pans and release the cakes. Pop the cakes into the freezer for 20 minutes to make it easier to slice. Then cut each cake in half horizontally. Set aside one of the top halves for the crumble decoration. We will only use 3 cake layers for assembling cake.
Whipped Cream Frosting:
In a mixing bowl, add in 8 oz cream cheese, 1/2 cup granulated sugar, and 1 tsp vanilla extract in a large mixing bowl. Fit the mixer with the whisk attachment and beat them together on medium speed until they are smooth.
While the mixture is still whipping, slowly add 2 cups of very cold heavy cream. Continue whipping until the frosting holds stiff peaks.
Assembling the Cake:
Place one of the 3 cake layers (bottom half of one of the cakes), cut side up on your serving plate or cake board. Spread and level some of the whipped cream frosting onto the cake layer until it is about 1/4" thick.
Place the second cake layer, cut side down on top of the bottom cake layer. Again, spread whipped cream frosting on top to cover the second layer, about 1/4" thick.
Place the third and final layer of cake on top (cut side down, so the top of the cake is as flat as possible). Spread whipped cream frosting to cover the top and sides of the cake. Remember to save some whipped cream frosting to make rosettes at the top of the cake in the end.
Crumble the last cake half in a food processor until they are fine crumbs. You can also crumble it by hand if you don't have a food processor. With your hands, place the crumbs on the sides and top of the cake, letting it stick to the frosting, until the entire cake is covered in these purple crumbs.
Put the remaining frosting in a piping bag with a large open star tip attached, and pipe out big rosettes around the cake's top edge, about 1 inch away from the edge, or in whatever pattern you'd like. Slice and enjoy!