Stir together coconut, pecans, brown sugar, condensed milk, melted butter, vanilla, and salt until thick. Set aside.

Sift flour, cocoa, baking powder, baking soda, and salt into a large bowl.

In another large bowl, whisk granulated sugar, brown sugar, eggs, oil, buttermilk, and vanilla until smooth.

Fold the dry ingredients into the wet mixture in two additions, then stir in hot coffee just until no streaks remain.

Preheat oven to 350°F (175°C). Grease a 10- to 12-cup bundt pan, dust with cocoa. Spoon two-thirds of the batter into the pan, dot with swirl mixture, and top with remaining batter. Swirl once or twice with a knife. Bake 45 to 55 minutes until a toothpick has moist crumbs. Cool 15 minutes in the pan, then invert onto a rack to cool completely.

Whisk powdered sugar, cocoa, 2 tbsp milk, and vanilla. Add more milk if needed. Drizzle over the cooled cake.