Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans and line the bottoms with parchment paper circles.
In the bowl of a stand mixer fitted with a paddle attachment, whisk together the flour, 1 3/4 cups sugar, cocoa powder, baking soda, baking powder, and salt. Add the buttermilk, oil, eggs, and 1 teaspoon vanilla; beat on medium speed for 2 minutes until the batter is smooth and well combined.
Carefully pour the hot coffee into the batter and mix on low speed until just combined; the batter will be thin. Divide the batter evenly between the two prepared pans.
Bake for 30 to 35 minutes, or until a wooden skewer inserted into the center of the cakes comes out clean. Let the cakes cool in the pans for 10 minutes, then invert them onto a wire rack to cool completely.
While the cakes cool, make the frosting. In a medium saucepan over medium heat, combine the butter, evaporated milk, 1 1/2 cups sugar, and egg yolks. Cook, stirring constantly, for about 12 minutes, until the mixture has thickened enough to coat the back of a spoon.
Remove the frosting from the heat and stir in the 1 1/2 teaspoons vanilla, chopped pecans, and flaked coconut. Continue to stir for another 5-7 minutes as it cools and thickens to a spreadable consistency.
Once the cake layers are completely cool, place one layer on a serving plate. Spread a generous layer of the pecan-coconut frosting over the top. Place the second cake layer on top and frost only the top of the cake with the remaining frosting, leaving the sides exposed.