Preheat oven to 350F (175C) and grease and flour the sides of two 8” cake pans (or spray with baking spray) and line the bottom with rounds of parchment paper.
Combine butter, oil, and sugar in the bowl of your stand mixer fitted with paddle attachment (or in a large bowl and use an electric mixer) and beat until ingredients are creamy and well-combined. 6 Tablespoons (85 g) unsalted butter, ⅔ cup (157 ml) avocado, vegetable, or canola oil, 2 cups (400 g) granulated sugar
Scrape down the sides and bottom of the bowl and then stir in sour cream, vanilla extract, and coconut extract.1 cup (240 g) sour cream, 2 teaspoons vanilla extract, ½ teaspoon coconut extract
In a separate, medium-sized bowl, whisk together flour, baking powder, baking soda and salt.2 ¾ cup (344 g) all-purpose flour, 1 teaspoon baking powder, ½ teaspoon baking soda, 1 teaspoon table salt
Using a spatula and stirring by hand, gradually, gently stir the dry ingredients into the wet (butter/sugar mixture) until completely combined. I'll usually add the dry ingredients in 3-4 parts. Scrape the sides and bottom of the bowl to ensure that all of your ingredients are well-combined. Set aside.
Pour egg whites into a medium-large sized glass or stainless steel bowl that is completely clean, dry, and grease-free. Using an electric mixer, beat on high-speed until stiff peaks form (meaning that if you remove the beater from the mixture, the peak that forms holds its shape and does not fold over or dissolve back in on itself).6 (190 g) large egg whites
Add the whipped egg whites to the batter and use a spatula to gently fold the egg whites into the batter. While you do not want to over-mix this batter, it is important that the egg whites are completely combined. Use a gentle hand and stir until you can’t see any streaks of egg whites in the batter.
Divide batter evenly into prepared cake pans.
Bake on 350F (175C) for 35-37 minutes or until a toothpick inserted in the center comes out mostly clean or with a few moist crumbs (no wet batter). Allow cakes to cool in pans for 10-15 minutes before running a knife around the edge to loosen the cakes and carefully inverting onto a cooling rack to cool completely before frosting.
FrostingHeat treat the flour: Place flour in a microwave-safe dish and heat for 30 seconds. Stir, then use an instant-read thermometer to check the temperature (must exceed 160F (71C)). If not warm enough, continue to heat in 10-second intervals until temperature is reached. Allow flour to cool completely before using (if it is lumpy, run it through a sifter before using). This "heat-treats" the flour in case it was contaminated. Set aside.4 Tablespoons (31 g) all-purpose flour
Combine butter and sugar in the bowl of a stand mixer fitted with a paddle attachment. Beat on medium-speed until creamy and well-combined.1 ¼ cup (282 g) salted butter, 1 ½ cups (300 g) granulated sugar
Add flour, one tablespoon at a time, beating on medium speed for 15 seconds after each addition. Scrape down sides and bottom of bowl and beat again for 20 seconds.
Add coconut milk and vanilla extract and stir to combine1 cup (236 ml) coconut milk, ¾ teaspoon vanilla extract
Turn mixer speed up to medium-high and beat for 6 minutes. Scrape down the sides and bottom of the bowl and beat again at least another 6 minutes, until frosting is smooth.
Test the frosting by tasting or rubbing between your fingers, it should not be gritty or grainy at all. If it still is, carefully scrape the sides and bottom of your mixing bowl again and stir again on high speed until no longer grainy.
Once your cakes are cool, ice them by placing one layer on your serving dish and applying an even layer of frosting to the top. Sprinkle liberally with some of the shredded coconut.3 cups (300 g) sweetened shredded coconut, divided
Place your second layer on top of the first and apply an even layer of frosting around the top and sides of the cake. Sprinkle remaining coconut over the top of the cake, and then use your hands to press coconut all around the sides.