1. Preheat the oven to 350°F (175°C) and prepare three 9-inch round cake pans by greasing and lining them with parchment paper.
2. Melt the sweet baking chocolate in a double boiler or microwave until smooth, then set it aside to cool slightly.
3. In a large bowl, cream together butter and sugar until light and fluffy.
4. Beat in egg yolks one at a time, ensuring each is fully incorporated.
5. Add the melted chocolate and vanilla extract to the creamed mixture and mix thoroughly.
6. In a separate bowl, sift together flour, baking soda, and salt.
7. Gradually add the dry ingredients and buttermilk alternately to the chocolate mixture, beginning and ending with the dry ingredients.
8. In another clean bowl, beat egg whites until stiff peaks form.
9. Gently fold the egg whites into the cake batter until just combined.
10. Divide the batter evenly among the prepared cake pans and smooth the tops.
11. Bake the cake layers in the preheated oven for 30-35 minutes or until a toothpick inserted in the center comes out clean.
12. Remove the cakes from the oven and let them cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.
13. To make the frosting, combine evaporated milk, sugar, egg yolks, and butter in a medium saucepan over medium heat.
14. Cook the mixture, stirring constantly, until it thickens, about 12 minutes.
15. Remove the frosting mixture from the heat and stir in shredded coconut, chopped pecans, and vanilla extract.
16. Allow the frosting to cool until it reaches a spreadable consistency, stirring occasionally.
17. Assemble the cake by placing one layer on a serving plate and spreading a generous amount of coconut-pecan frosting on top.
18. Add the second cake layer and frost the top with more coconut-pecan frosting.
19. Place the final cake layer on top and spread the remaining frosting over the top of the cake.
20. If desired, coat the sides of the cake with chocolate frosting or leave them uncovered for a rustic look.
21. Decorate the cake with pecan halves, additional coconut flakes, or maraschino cherries for garnish if desired.
22. Serve the German Chocolate Cake at room temperature and enjoy.