Preheat the oven to 325 degrees . Butter a 9-by 13-inch metal cake pan. Line with parchment and butter the parchment.
In a medium saucepan, bring 2/3 cup water to a boil. Whisk in the cocoa powder until smooth. Whisk in the butter and chocolate over low heat until melted, about 2 minutes. Remove from the heat and whisk in 1 1/2 cups granulated sugar, 2 teaspoons vanilla and 1/2 teaspoon salt. Whisk in the eggs, 1 at a time, beating well after each addition.
In a large bowl, stir the flour, baking powder and baking soda together. Make a well in the center, pour in the chocolate mixture and stir until smooth. Stir in 1 packed cup coconut. Scrape the batter in the prepared pan and bake in the lower third of the oven for about 30 minutes or until firm in the center. Let cool in the pan on a rack for 10 minutes, then invert onto rack to cool completely. Leave the oven on.
While the cake cools, spread the almonds on a rimmed baking sheet and bake for 12 minutes or until toasted; let cool.
In a medium saucepan, combine 3/4 cup cream, the remaining 3/4 cup sugar and the remaining pinch salt and simmer, stirring, over medium heat until the sugar is dissolved, about 3 minutes. Remove from the heat and stir in the remaining 2 teaspoons vanilla and 3 packed cups coconut. When cool, fold 1 1/2 cups almonds into the coconut mixture.
Place the cake layer on a tray or platter and spread the coconut-almond evenly on top. Cover the cake with plastic wrap and refrigerate for about 4 hours to firm up.
Whip the remaining 2 1/4 cups cream with the confectioners sugar until stiff but not dry. Spread over the top and sides of the cake to cover. Sprinkle the top with the remaining almonds.