Preheat oven to 350°. Grease and flour three 9-inch cake pans, then line them with waxed paper, cut to fit. Grease and flour the waxed paper or spray with Pam.
Melt the chocolate in the boiling water. Set aside.
Sift together the flour, baking soda and salt. Set aside.
Beat the egg whites until stiff peaks form.
In the large bowl of an electric mixer, cream butter and sugar, allowing mixer to run for 5 minutes. Add egg yolks, one at a time, beating well after each addition. Let mixer run an additional 2 minutes. With mixer running, add vanilla and chocolate/water mixture.
Add dry ingredients alternately with the buttermilk, combining well. Gently fold the stiffly beaten egg whites into cake batter.
Pour the batter into the three prepared cake pans. Bake at 350°F for 30 to 35 minutes or until a cake tester comes out clean. Cool on racks. Frost top and fill between layers with Coconut-Pecan Frosting.
Combine the evaporated milk, sugar, egg yolks, butter and vanilla. Cook and stir over medium heat until thickened, about 12 to 15 minutes. Add coconut and chopped pecans. Cool until thick enough to spread, beating occasionally. Makes about 3 cups of frosting.