Step 1: Preheat your oven to 350°F (175°C). Grease and flour three 9-inch round cake pans. Line the bottoms with parchment paper for easy release.
Step 2: In a small saucepan over low heat, melt the German sweet chocolate with 1/2 cup of water, stirring until smooth. Set aside to cool slightly.
Step 3: In a large bowl, cream together the softened butter and granulated sugar until light and fluffy. Beat in the egg yolks one at a time, ensuring each is fully incorporated before adding the next. Stir in the cooled melted chocolate and vanilla extract.
Step 4: In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.
Step 5: Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined; do not overmix.
Step 6: In a clean, separate bowl, beat the egg whites until stiff peaks form. Gently fold the beaten egg whites into the cake batter.
Step 7: Divide the batter evenly among the prepared cake pans. Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes before inverting them onto wire racks to cool completely.
Step 8: While the cakes are cooling, prepare the frosting. In a medium saucepan, combine the evaporated milk, granulated sugar, beaten egg yolks, and butter. Cook over medium heat, stirring constantly, until the mixture thickens and comes to a boil. Remove from heat.
Step 9: Stir in the vanilla extract, shredded coconut, and chopped toasted pecans. Mix well. Let the frosting cool to room temperature, stirring occasionally. It will thicken as it cools.
Step 10: Once the cake layers are completely cool and the frosting has thickened, place one cake layer on a serving plate or cake stand. Spread about one-third of the coconut-pecan frosting evenly over the top.
Step 11: Carefully place the second cake layer on top, and spread another third of the frosting. Repeat with the third cake layer and the remaining frosting.
Step 12: If desired, decorate the sides of the cake with additional toasted pecans. Allow the cake to set for at least an hour before slicing and serving.