Preheat the oven to 350 degrees.
Spread the coconut and almonds on separate baking sheets and toast, stirring occasionally, just until golden brown, 10 to 15 minutes. Set aside to cool.
Line the bottom and sides of a 14 by 17-inch baking sheet (with sides) with parchment or waxed paper. Sift together the sugar, flour, cocoa, baking powder, baking soda and salt. Transfer to a mixer fitted with a whisk attachment (or use a hand mixer) and blend briefly.
In a medium bowl, whisk together the eggs, milk, oil and vanilla extract. Add to the dry ingredients and mix at low speed for 5 minutes. Gradually add the hot water, mixing at low speed just until combined. The batter will be quite thin. Pour the batter into the prepared pan. Bake until a tester inserted in the center of the cake comes out clean (a few crumbs are okay), 25 to 30 minutes. Let cool in the pan.
Caramel: Pour the sugar into the center of a deep saucepan. Carefully pour the water around the sugar, trying not to splash any sugar onto the sides of the pan. Do not stir; gently draw your finger through the center of the sugar to moisten it. Over medium-high heat, bring to a boil without stirring. Reduce the heat to a fast simmer and cook without stirring until amber-caramel in color, 10 to 20 minutes. Immediately remove from the heat. Using a wooden spoon, slowly and carefully stir in the cream (it will bubble up and may splatter). Stir in the toasted coconut and almonds. Set aside.
When ready to serve, cut the room-temperature cake in the pan into 6 even strips, each 3 inches wide. Using diagonal strokes of the knife, cut each strip into 4 triangles. If the sauce has stiffened, rewarm it over low heat (or in a microwave) until softened. Place a triangle on each plate, drizzle with sauce, and rest another triangle on top at a different angle. Drizzle with more sauce and serve.
Courtesy Gale Gand, "Butter Sugar Flour Eggs"; by Gale Gand, Rick Tramonto, Julia Moskin, Clarkson N. Potter Publishers, 1999