Preheat the oven to 350°F (175°C).
Grease and flour three 9-inch round cake pans.
In a large mixing bowl, combine the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
Add the buttermilk, vegetable oil, eggs, and vanilla to the dry ingredients, mixing until just combined.
Divide the batter evenly among the prepared cake pans.
Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cakes to cool in the pans for 10 minutes, then turn them out onto wire racks to cool completely.
While the cakes are cooling, prepare the frosting by combining shredded coconut, chopped pecans, sweetened condensed milk, and butter in a saucepan.
Cook the mixture over medium heat, stirring constantly until the mixture thickens.
Remove from heat and let the frosting cool to room temperature.
Once cakes are cool, spread frosting between each layer and on top of the cake.
Garnish with additional pecans and coconut if desired.
