Preheat the oven to 325°F (163°C). Grease three 9-inch cake pans with butter or line them with parchment paper.

In a large mixing bowl, beat 6 egg yolks until pale and creamy. Gradually mix in 1.5 cups of granulated sugar, then add 0.5 cup of buttermilk.

Sift in 1.5 cups of cake flour and 2.25 teaspoons of baking powder, folding gently to maintain airiness.

In a separate bowl, whisk 6 egg whites until stiff peaks form. Gently fold into the yolk and flour mixture.

Divide the batter among the prepared cake pans and bake for 30 minutes or until golden brown.

Remove from oven and let cool in pans for 5 minutes before inverting onto wire racks to cool completely.

For the frosting, beat 1.25 cups of softened butter until creamy, then mix in 4 cups of powdered sugar, coconut extract, vanilla extract, and heavy cream or milk.

To assemble, place one cake layer on a plate, spread frosting on top, add the second layer, and repeat. Cover the whole cake with remaining frosting.

Decorate with toasted coconut flakes and optional edible flowers.