This was lightly adapted from my ube chiffon cake recipe. Since I was planning to bake it in a 9” x 13” dish, I knew I didn’t have to worry too much about the batter being too heavy for the pan like when I baked the chiffon version. Hence, I upped the ube powder slightly to ensure a more vibrant color and since I still wanted a lighter texture cake, I decided to proceed with the chiffon cake concept of whipping the egg whites separately before folding it into the rest of the batter. The result was a beautiful, deep purple color cake that is moist but light and so delicious that you’ll want to inhale the entire cake, lol. Enjoy!
Note: this recipe produces a not too sweet cake or frosting, just the way we like it.
1-1/4 cups Authentic Foods Steve’s GF Cake Flour*^
1/4 cup plus 1 tablespoon purple sweet potato powder*^
1-1/4 cups sugar, divided
1 tablespoon baking powder
1/2 teaspoon salt
7 large eggs, separated
1/2 cup vegetable oil
1 cup first pressing/unsweetened coconut milk
1/2 teaspoon cream of tartar
*To measure the flour and sweet potato powder, spoon them into appropriate measuring cups/spoon and level them with the back of a knife.
^I have not made this recipe using regular wheat flour but the gluten-free flour I used is meant to replace wheat flour cup per cup. The purple sweet potato powder I utilized here is the T’S Moment brand found on Amazon – the texture is much finer than the ube powder I’ve seen at some Asian stores.
Adjust oven rack to the middle position and heat oven to 350F. In a large bowl, whisk flour, sweet potato powder, 1/2 cup sugar, baking powder, and salt together. Make a well in the center, and add the yolks, oil, and coconut milk. Stir or whisk until combined.
With an electric mixer, whip egg whites and cream of tartar on medium-low speed until foamy. Then increase mixer speed to medium-high, gradually add the remaining 3/4 cup sugar, and continue whipping until soft peaks form. Mix 1/3 of the whipped egg whites into the flour mixture with a large rubber spatula until combined (this helps to lighten the batter). Then carefully fold in the remaining egg whites.
Pour batter into an oiled 9” x 13” baking dish and bake for 45 minutes or until a toothpick/skewer inserted into the center comes out clean. Remove baking dish to a cooling rack and let cake cool completely. Once cooled, top cake with whipped cream frosting and sprinkle with toasted shredded coconut.
Toasted coconut topping
1 cup unsweetened shredded coconut
Place the coconut in a medium baking sheet lined with foil. Spread the coconut in a single layer and bake at 350F for 2 to 3 minutes, stirring every minute until the coconut is toasted. Remove from oven and transfer to a dish to cool completely.
Whipped cream frosting
1/4 cup water
1 (1/4-oz) envelope Knox unflavored gelatin
2 cups heavy cream, divided
1/2 cup sour cream
1/4 cup powdered sugar
2 teaspoons vanilla extract
Place water in a small prep bowl. Sprinkle gelatin evenly onto the water, and set aside for a few minutes until all the water is absorbed. Microwave the gelatin mixture on high until melted, about 15 seconds. Add 3 tablespoons heavy cream to the melted gelatin and stir. Set aside for a moment (if it sets, just microwave the mixture again, 5 seconds at a time). Begin whisking the remaining heavy cream, sour cream, sugar, and vanilla together (I use a stand mixer with the whisk attachment) until soft peak. Slowly pour in the gelatin mixture and continue to whisk until peaks are firm enough to hold their shape. Refrigerate if not using immediately.