Make the cake: Position a rack in the center of the oven and preheat to 325 degrees F. Butter two 9-inch-round cake pans and line the bottoms with parchment paper. Whisk the flour, baking powder, baking soda and salt together in a medium bowl.
Melt the 12 tablespoons butter in a medium saucepan over medium heat. Whisk in the cocoa powder and cook for 1 minute. Remove from the heat, add the muscovado and granulated sugars and whisk until the sugar has dissolved. Add the coffee, buttermilk, eggs and vanilla extract and continue whisking until smooth and just combined. Add the dry ingredients and stir until the batter is smooth.
Divide the batter evenly between the prepared cake pans and bake until a toothpick inserted into the center comes out with a few moist crumbs attached, 40 to 45 minutes. Let the cakes cool in the pans on a wire rack for 20 minutes. Invert the cakes onto the wire rack and let cool at least 1 hour before frosting.
Make the frosting: Combine the whole milk, coconut milk and goat's milk in a small saucepan and bring to a simmer over low heat. Keep warm while you prepare the caramel.
Combine the sugar and 1/4 cup water in a medium saucepan over high heat and cook without stirring until a deep amber color, 8 to 10 minutes. Slowly and carefully whisk in the warm milk mixture and continue whisking until smooth. Add the vanilla seeds and corn syrup. Bring to a boil, reduce the heat to medium and cook, stirring occasionally with a wooden spoon, until the sauce is reduced by half and the consistency of a caramel sauce, about 55 minutes.
Remove from the heat and whisk in the butter, vanilla extract, salt and rum (if using). Transfer the sauce to a medium bowl and stir in the pecans and shredded coconut. Let the frosting cool to room temperature, stirring it occasionally, before frosting the cake.
To assemble the cake, slice each cake in half horizontally. Place 1 cake layer on a cake round and spread one-third of the frosting evenly over the top. Repeat to make 3 layers, then top with the remaining cake layer, top-side up.
Make the ganache: Bring the cream to a simmer in a small saucepan. Put the chocolate in a medium heatproof bowl, add the hot cream and the corn syrup and let sit for 30 seconds. Gently whisk until smooth. Let sit at room temperature for 10 minutes.
Set the cake on a wire rack placed over a rimmed baking sheet. Pour the chocolate ganache over the cake, letting the excess drip down the sides. Sprinkle the top with toasted coconut and pecans. Let sit at room temperature for at least 30 minutes and up to 4 hours before slicing.
Slice the cake and top with a dollop of Coconut Whipped Cream.
Photograph by Yunhee Kim
Recipe courtesy Bobby Flay for Food Network Magazine