To make the filling:

1. In a large saucepan, combine the egg yolks, evaporated milk and vanilla extract and whisk until well combined.
2. Add the sugar and butter and cook on medium heat for 12-15 minutes, or until thickened and slightly pudding-like, stirring constantly.
3. Remove from heat and stir in shredded coconut, pecans and salt.
4. Pour into a heat-proof bowl and set in the fridge to cool completely.

To make the cake layers:

1. Prepare three 9-inch cake pans with parchment paper circles in the bottom and grease the sides. Preheat oven to 350°F (176°C).
2. Heat the water in the microwave just until it begins to boil. Pour the hot water over the chopped chocolate. Let it sit for 2-3 minutes, then stir until melted and smooth. If it doesn’t melt completely, heat in the microwave for another 10-15 seconds, then stir until smooth. Set aside.
3. Combine flour, baking soda and salt in a medium sized bowl. Set aside.
4. In a large mixing bowl, cream butter and sugar together until light in color and fluffy, about 2-3 minutes. Do not skimp on the amount of creaming time.
5. Add the egg yolks one a time, mixing until well combined after each. Add the vanilla extract and sour cream and mix until well combined.
6. Add the melted chocolate mixture from above and mix until well combined, scraping down the sides of the bowl a time or two to make sure things are well incorporated.
7. Add half of the dry ingredients to the batter and mix until well combined. Add the buttermilk and mix until well combined. Add remaining dry ingredients and mix just until well combined. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated. Set aside.
8. Add the egg whites to a large mixer bowl and whip on high speed until stiff peaks form.
9. Gently fold about half of the whipped egg whites into the rest of the cake batter until mostly combined, then add the remaining egg whites and gently fold until well combined.
10. Divide the batter evenly between the prepared cake pans and bake for 20-25 minutes, or until a toothpick inserted in the middle of the cakes comes out clean.
11. Remove the cakes from the oven and allow to cool for 2-3 minutes, then remove to a cooling rack to finish cooling.

To finish the cake:

1. When the cake and filling have cooled completely, make the frosting and finish the cake. Add the butter to a large mixer bowl and beat until smooth.
2. Add the cocoa powder and half of the powdered sugar and mix until well combined and smooth.
3. Add the melted chocolate in 2-3 batches and mix until well combined and smooth.
4. Add the salt and 3 tablespoons of heavy cream and mix until well combined and smooth.
5. Add the remaining powdered sugar and mix until well combined and smooth.
6. Add the remaining heavy cream, as needed, to get the right consistency of frosting.
7. To build the cake, first use a large serrated knife to remove the domes from the tops of the cakes so they are flat. See my tips on how to level a cake and how to stack a cake.
8. Place the first cake layer on a serving plate or on a cardboard cake circle.
9. Pipe a dam of chocolate frosting around the outside of the cake layer. Spread about 1/3 of the coconut pecan filling evenly on top of the cake, in the center of the dam.
10. Add the second layer of cake, another dam of frosting and add another 1/3 of the coconut pecan filling.
11. Add the third layer of cake on top, then frost the outside of the cake with the remaining chocolate frosting.
12. Pipe a shell border around the top outer edge of the cake. I used Ateco tip 847. Fill in the border with the remaining 1/3 of the coconut pecan filling. Decorate the bottom of the cake with pecans, if desired.
13. Refrigerate until ready to serve. This cake is best served cool, but not super cold. Store in an air-tight container or well covered. Best if eaten within 4-5 days.