Preheat the oven to 350°F (175°C). Grease and flour two round cake pans.

In a large bowl, cream together the butter and sugar until light and fluffy.

Add the egg whites one at a time, beating well after each addition.

Mix in the vanilla extract.

In a separate bowl, combine the flour and baking powder. Gradually add to the creamed mixture, alternating with milk, beginning and ending with the flour mixture. Mix until just combined.

Divide the batter evenly between the prepared pans.

Bake in preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cakes to cool in the pans for 10 minutes before transferring to wire racks to cool completely.

In a saucepan over medium heat, combine the brown sugar, heavy cream, and egg yolks. Cook, stirring continuously until thickened.

Remove from heat, and stir in the coconut and pecans. Let cool before using.

Once the cakes are completely cool, place one layer on a serving plate and spread a layer of frosting on top.

Top with the second cake layer and frost the top and sides with the remaining coconut pecan frosting.