Step 1: Prepare the Cake

Begin by preheating the oven to 400°F (200°C). Grease a 13x18 inch sheet pan thoroughly. In a sizable mixing bowl, blend the all-purpose flour, granulated sugar, and cocoa powder, whisking until the mixture is homogeneous.

Step 2: Melt the Chocolate Mixture

In a saucepan, combine the water, unsalted butter, vegetable shortening, and the chopped German chocolate. Heat over medium, stirring regularly until the mixture is fully melted and smooth.

Step 3: Combine Ingredients

Pour the melted chocolate blend into the bowl containing the dry ingredients. Whisk until fully combined. Then, incorporate the buttermilk, baking soda, salt, eggs, and vanilla extract, continuing to whisk until the batter is smooth.

Step 4: Bake the Cake

Transfer the batter into the prepared sheet pan, ensuring it is evenly spread. Bake for 20 to 22 minutes, or until a toothpick inserted into the center comes out clean. Once done, allow the cake to cool completely in the pan.

Step 5: Make the Frosting

To prepare the frosting, combine the evaporated milk, egg yolks, unsalted butter, light brown sugar, and granulated sugar in a saucepan. Bring to a simmer over medium heat while stirring frequently. Once it reaches a simmer, continue cooking for an additional 10 to 12 minutes, stirring constantly until the mixture attains a spoonable consistency.

Step 6: Add Coconut and Pecans

Remove the saucepan from heat and stir in the sweetened shredded coconut, chopped pecans, and vanilla extract. Allow the frosting to cool slightly for about 5 to 10 minutes until it is no longer extremely hot.

Step 7: Frost the Cake

Pour the frosting over the cooled cake, using an offset spatula to spread it evenly across the top. For optimal results, refrigerate the frosted cake for 1 to 2 hours before slicing and serving. Enjoy!