Preheat oven to 350 degrees F (175 degrees C). Grease and flour one 9x13 inch baking pan very well!
Sift flour and baking powder together in a small bowl, set aside.
Cream the butter or margarine and the 1 cup sugar together until well blended.
Add egg whites and the 1/2 teaspoon vanilla extract and beat for about 4 minutes on high.
Add the egg yolks and beat on medium, just until well combined.
Add the flour mixture to the butter mixture a little at a time, mix until well blended (you may need to scrape the bowl with a spatula after each addition.
Pour batter into prepared pan.
Bake at 350 degrees F (175 degrees C) for 30 minutes or until a knife inserted into the center comes out clean. Let cool.
Pierce cake several times with a fork, chopstick, or skewer. Really...lot's of holes!
Whisk the coconut milk, condensed milk, and evaporated milk together.
Slowly pour over the top of the cooled cake.
Whip whipping cream, the 1 cup of powdered sugar. and the additional 1 teaspoon vanilla together until thick--about 5 minutes at high speed. (watch it though, too long and you have butter!)
Spread over the top of cake. Chill in the fridge for at least 1 hour before serving, the longer the better!