Preheat the oven to 325°. Butter two 9-inch round cake pans. Line the bottoms with parchment paper, then butter and flour the paper.
In a small bowl, whisk the cake flour with the cinnamon, nutmeg and salt. In a measuring cup, stir the buttermilk with the vanilla extract and baking soda until combined. In the bowl of a standing electric mixer fitted with the paddle, beat the softened butter with the sugar until fluffy. Add the egg yolks and beat until they are incorporated, then beat in the melted chocolate, scraping down the side and bottom of the bowl as necessary. Beat in the dry and wet ingredients in 3 alternating batches, scraping down the side of the bowl occasionally.
Transfer the cake batter to a large bowl and wash out the mixing bowl. Add the egg whites to the mixing bowl and beat with the whisk until soft peaks form. Fold the beaten egg whites into the chocolate batter until no streaks remain.
Divide the batter evenly between the prepared pans and bake the cakes for 45 to 50 minutes, until a toothpick inserted in the centers comes out with just a few moist crumbs attached. Let the cakes cool slightly on a wire rack, then invert the cakes and peel off the parchment paper. Let the cakes cool completely.
Spread the pecans on a pie plate and toast for about 12 minutes, until they are fragrant. Let cool, then coarsely chop 1 cup of the nuts, leaving the rest whole. In the bowl of a standing mixer fitted with the whisk (or using a handheld electric mixer), beat the softened butter with the confectioners' sugar and cocoa powder until combined. Add the vanilla extract and hot coffee and beat the frosting until fluffy. Fold in the 1/2 cup of shredded coconut and the chopped toasted pecans.
Place a cake layer on a plate and spread half of the frosting on top. Cover with the second cake layer and spread the remaining frosting on the top. Garnish the cake with shredded coconut and the whole toasted pecans. Cut the cake into wedges and serve.