Spray 3 8-inch round cake pans with baking spray. Set aside.
In a large bowl, combine flour, sugar, baking powder, salt, and coconut. Set aside.
In a medium bowl, whisk together cream of coconut, milk, vegetable oil, egg yolks, and vanilla. Set aside.
In a small bowl, beat egg whites with an electric mixer to medium peaks. Set aside.
Pour wet ingredients into dry ingredients and mix thoroughly.
Fold in egg whites.
Divide evenly into prepared pans.
Bake for 25 minutes, or until cake tests done.
In a medium bowl, combine egg yolks, corn starch, and sugar.
Stir together gently with a wooden spoon. Do NOT beat.
Continue stirring until mixture smooths out. Set aside.
Heat milk until it just starts to bubble around the edges.
Slowly pour milk into egg yolk mixture, stirring constantly.
Return mixture to pot and cook over medium low heat until it starts to thicken, about 2 minutes.
Remove from heat and whisk in butter.
Strain through a fine mesh sieve into a clean bowl.
Stir in coconut and vanilla.
Cover with a piece of plastic wrap touching the top of the custard.
Refrigerate until needed.
Beat butter until light and fluffy.
Gradually beat in powdered sugar.
Stir in vanilla and heavy cream.
Putting It Together
Level cake layers.
Place one layer on cake plate.
Pipe a ring of frosting around the outside of the cake layer.
Spoon half of custard into the center and spread evenly on top within the ring of frosting.
Add another cake layer and repeat topping.
Add last cake layer and spread with remaining frosting.
Sprinkle coconut on top and press around sides of cake.
While whipping the egg whites, be sure to not over whip! You don’t want to dry them out. You can use the whisk attachment (or even a rubber spatula) to stir the egg whites around to see if they’re properly whipped.
When folding the egg whites into the cake batter, be very careful not to deflate them! The whipped egg whites are what make the cake so light and airy.
Leveling these cakes can be a little tough because of the coconut inside the cake. So, make sure you have a sharp serrated knife and you can get on eye-level with the cake layer to make sure you’ve cut them straight. Always try to be gentle with it. Begin by cutting at the base of the dome. If it’s level after cutting that, you’re good to go! But, if it’s not, just cut small amounts until it is. Don’t be afraid of trimming it!
When making the pastry cream, make sure the egg yolk, corn starch, and sugar mixture is smooth and liquid-y consistency. You don't want it lumpy!
Make sure you whisk in the butter while the mixture is still hot! The butter needs to melt and be mixed in thoroughly.
Don't skip straining the pastry cream! You don't want to bite into a little bit of cooked egg.
When making the buttercream, the butter needs to be room temperature.