Make the Hot Milk Cake as directed and make sure it is cool inside and out. (If frozen, let thaw in the refrigerator, 3 to 4 hours. or on the countertop for 1 to 2 hours. If time demands, you can thaw on the countertop. If time demands you can thaw on the countertop 1 to 2 hours, but be careful not let it sit too long before you begin working with it, as a cold cake is easier to cut.)
Clear a space in the refrigerator large enough for the cake on a cake board. The mousse cake will need several hours to set up.
If making the Coconut Simple Syrup now, let cool to room temperature. Make the Coconut Mousse as directed, allowing time for the gelatin-sugar mixture to cool before finishing.
Set a revolving cake stand on a clean, dry work surface and place the cake, top-side up, on the stand. Using a serrated knife and holding the blade perfectly horizontal, remove any curve from the top of the cake to level it. While you saw gently with the knife, use your other hand to rotate the stand gradually and bring the cake toward you. Get eye level to the cake as needed to make sure you are holding the knife exactly level. Repeat to split the cake into three or four equal layers.
Arrange all the cake layers on the work surface. Using your hands, tap off and brush away excess crumbs. Turn the original bottom layer flat-dark-side, or pan-side, up; reserve this to be the top layer of the assembled cake. Using a pastry brush, brush the top of each layer with an ample amount of the coconut syrup.
Line a clean 6-by-3-inch cake pan with plastic wrap, leaving about 3 inches of overhang all around the sides to use later as a handle. Take up the original top of the cake, which you leveled, to be the bottom layer of the assembled cake. Place the first layer of cake, syrup-side up, in the lined pan. Scoop 1/2 to 3/4 cup of the mousse on top of the cake layer and use an offset spatula to level it. Top with the second layer of cake, syrup-side up, and press down lightly to seal and secure. Add another layer of mousse. Repeat with the third layer if making a four-layer cake.
Place the reserved top piece, flat-dark-side up, on top. Cover with plastic wrap and carefully transfer the cake to the refrigerator. Let set for at least 3 hours and up to 2 days.
To unmold the mousse cake, wrap a hot towel around the pan for 1 minute and gently shake to loosen the cake. Invert the pan onto a cake board on a clean work surface, then gently lift the pan off. If it resists, give a little tug on the plastic-wrap "handle." When the pan is off, peel the plastic-wrap lining from the cake. Transfer the cake on its board onto the revolving cake stand, with a nonslip pad or damp paper towel underneath.
This cake requires only one coat of icing. Using the offset spatula, smear a generous scoop of the icing on one side of the cake. Keeping the spatula in front of you, rotate the cake stand to spread the icing in a smooth coat about 1 inch thick. (It needs to be thick enough to hide the sides of the cake, but not drooping down the sides.) Add more icing as you go, but do NOT back track! The icing will be covered with coconut, so it is not important for it to be perfect; however, you want the cake layers aligned perfectly and the coat of icing to be straight up and down on all sides, as well as crumb free and smooth. As you frost the sides, push the icing up over the top edge of the cake to make sure the coverage is complete, then use this excess to frost the top, using the spatula to pull the icing across the cake toward the center. There should be enough icing from the sides to cover the top, but if necessary, add another small scoop.
Using a cupped hand, apply the dried coconut to the sides and top of the cake, pressing gently to help it adhere. Very carefully transfer the cake on the board to a presentation platter. Gather up any excess coconut and press it onto the cake, or reserve for another use. Refrigerate the cake for at least 1 hour and up to 8 hours. Remove from the refrigerator 30 minutes before serving.
Stir 1/2 cup coconut milk into 1/2 cup Simple Syrup. Store tightly sealed in the refrigerator for up to 1 month.
Photograph by Frankie Frankeny
Reprinted with permission from Miette by Meg Ray with Leslie Jonath, Chronicle Books copyright (c) 2011