• Preheat the oven to 350°F (175°C) and grease and flour three 9-inch round pans.
• Sift together 2 1/2 cups of cake flour, 1 teaspoon of baking soda, and 1/2 teaspoon of salt and set aside.
• In a small saucepan, heat 1/2 cup of water and 4 ounces of German sweet chocolate until melted. Remove from heat and let cool.
• In a large bowl, cream 1 cup of softened butter and 2 cups of white sugar until light and fluffy.
• Beat in the 4 egg yolks one at a time, then add the melted chocolate mixture and 1 teaspoon of vanilla extract.
• Beat in the flour mixture alternately with 1 cup of buttermilk, making sure to mix only until incorporated.
• In a separate large glass or metal mixing bowl, beat 4 egg whites until stiff peaks form.
• Fold 1/3 of the egg whites into the batter, then quickly fold in the remaining egg whites until no streaks remain.
• Pour the batter evenly into the three 9-inch pans.
• Bake in the preheated oven for 30 minutes, or until a toothpick inserted into the center of the cake comes out clean.
• Allow to cool for 10 minutes in the pan, then turn out onto a wire rack.

For the filling:

• In a saucepan, combine 1 cup of white sugar, 1 cup of evaporated milk, 1/2 cup of butter, and 3 beaten egg yolks.
• Cook over low heat, stirring constantly, until thickened.
• Remove from heat and stir in 1 1/3 cups of flaked coconut, 1 cup of chopped pecans, and 1 teaspoon of vanilla extract.
• Let cool until thick enough to spread.
• Spread the filling between the layers and on top of the cake.
• In a small saucepan, melt 1/2 teaspoon of shortening and 1 square of semisweet chocolate. Stir until smooth, then drizzle down the sides of the cake.