Preheat oven to 350 degrees. Line bottoms of three, 8 inch round cake pans with parchment paper. Butter and flour sides of pans (I use Baking PAM to do this).

Use mixer on medium speed to beat butter and sugar together until lightened and fluffy, about 2 minutes.

On low speed, beat in egg whites, one at a time. Scrape down sides of bowl with a spatula as needed. After egg whites are mixed in, mix in vanilla extract.

In a small bowl, whisk together flour, cornstarch, salt, and baking powder.

Alternate beating in flour mixture and coconut milk, in about 3-4 additions each, starting and ended with flour mixture.

Fold in sour cream and coconut flakes until well combined.

Divide batter evenly between three prepared pans. Bake until tops are a light golden color and a toothpick inserted into the center of the cake comes out with just a few crumbs, about 20-22 minutes.

Let cakes cool in pan for at least 5 minutes before removing. Allow cakes to cool completely before frosting.

If needed, when cakes are cooled, use serrated knife or cake leveler to level cakes.

Use electric mixer with paddle attachment to beat butter and shortening until lightened and fluffy, about 1-2 minutes.

Mix in salt and vanilla extract.

Alternate mixing in powdered sugar, in 1/2 to 1 cup increments, and coconut milk, in 1/2 to 1 tbsp increments, until desired taste and consistency are reached.

Use frosting between cake layers and around the outside of the cake. Use your hands to gently press coconut flakes all over the top and sides of the frosting.