CHOCOLATE SAUCE FOR GARNISH:
Prepare the chocolate cream: The base of the chocolate cream is a creme anglaise, which is poured over chocolate to make a ganache.
Pour half of the sugar into a small mixing bowl and set the remaining sugar aside. Add the egg yolks and whisk until well combined. The mixture should be thick, smooth, and homogenous.
Pour the heavy cream, milk, and remaining sugar into a non-reactive 3-quart heavy-bottomed saucepan, place it over medium-high heat, and bring to a boil. Temper the egg mixture with the hot mixture by carefully pouring about 1/3 of the hot mixture into the egg mixture. Whisk immediately to keep the eggs from scrambling. Pour the tempered egg mixture back into the saucepan and place over medium heat, stirring constantly with a rubber spatula. The liquid will begin to thicken. When it reaches 182 degrees on a candy thermometer and is thick enough to coat the back of a spoon, it is finished and should be removed from the heat. If you do not have a thermometer, you can tell that it is finished by using the following method: In one quick motion, dip the spatula into the creme anglaise and hold it down horizontally in front of you. With the tip of your finger, wipe a clean line down the center of the spatula. If the trail keeps its shape, the creme anglaise is ready. If the trail fills with liquid, cook it for another minute and repeat the test. The objective is to remove the creme anglaise from the heat just before it boils. If the creme anglaise boils, the egg yolks will scramble. If this happens, you can still use it if you mix it with a hand-held immersion blender, food processor, or a blender. You will need a blade to liquefy the scrambled egg pieces. Remove from the heat.
Place the chopped chocolate in a medium-size mixing bowl and make a ganache by pouring the creme anglaise over the chocolate in two or three additions. Use a hand whisk to incorporate fully after each addition. The ganache should be thick, shiny, and smooth. Whisk in the Grand Marnier. Place in the refrigerator to cool and set. As the cream cools, the cocoa butter in the chocolate will harden and hold everything together. The cream will also become more flavorful as it cools. If you have time, make this a day in advance to give the chocolate flavor time to develop. (The chocolate cream can be stored in the refrigerator, tightly covered with plastic wrap, for up to 3 days.)
Prepare the tuiles: Preheat the oven to 375 degrees. Combine the coconut, sugar, eggs, and butter in a medium-size mixing bowl and mix with a hand whisk until well combined. Place a silicon mat on a baking sheet. (If you do not have a silicon mat, you can use a nonstick baking sheet.) Use a small offset spatula dipped in water to spread 4-inch circles of the tuile batter on the mat or baking sheet. Place in the oven and bake until evenly light golden brown, 8 to 10 minutes. Allow the tuiles to cool on a wire rack.
Assemble the Napoleon: Place one tuile in the center of each plate. Dip a large spoon in hot water and roll it through the chocolate cream to form a quenelle, or egg-shaped scoop, of chocolate cream. Place the chocolate cream in the center of the tuile and repeat for the remaining plates. Top with a second tuile and another quenelle of chocolate cream. Top each with a third tuile. Garnish the plate with the chocolate sauce and creme anglaise. You could also use fresh berries in season or chocolate shavings. Serve immediately.