Combine flour and cornstarch. Combine butter and vanilla. Set them both aside. Preheat the oven to 400 degrees. Grease and flour a rectangular cake pan. 9x13 Bring a small pot of water to a simmer on the stove.
In the bowl of a stand mixer, combine eggs and sugar. Place the bowl on top of the simmering pot of water. Whisk constantly until the mixture reaches 110 degrees. Remove from the heat and place on the mixer with whisk attachment. Whip the egg mixture to full volume. Soft peak. Fold in the flour mixture. Then fold in the butter mixture. Pour into the cake pan and smooth the surface. Bake for 15 minutes or until a toothpick comes out clean.
3 milks
Whisk together the 3 milks and the vanilla. Poke many holes in the cake with a fork or toothpick. Pour the milks over the cake and allow to sit overnight.
Whipped Cream
Preheat the oven to 350 degrees. Toast the coconut for 5-8 minutes and allow to cool. Whip the cream, sugar, and vanilla together until stiff peaks form. Spread the cream over the cake. Top with toasted coconut and serve.