I recommend using a #789 cake decorator tip to cover the cake with caramel frosting. The caramel frosting is thick and almost fudge-like, so it's not easy to spread but it pipes just fine! Also, since this cake is double frosted, use a 9-inch cake stand or larger for display.
1cupunsweet cocoa powdersifted (I used Dutch-processed but natural is okay too)
2tablespoonscoffee dissolved in 2 tablespoons hot water
Gold luster dust
Flake sea salt for sprinkling
6macaronsuse my homemade recipe or buy them ready-made
Make the butter cake: Preheat the oven to 350°F. Grease three 8-inch (or 9-inch) cake pans with vegetable shortening or cooking spray and line the bottoms with parchment rounds.
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar until lightened in color and fluffy, 4-5 minutes. Add the eggs, one at a time, mixing well after each addition. Mix in the vanilla extract. Sift together the flour, baking powder, and salt. Add the flour mixture to the butter mixture in 3 additions, alternating with the milk, begin and end with the flour mixture, and beat after each addition until well combined. Beat until the batter is smooth and thoroughly combined.
Bake for 25-30 minutes or until a skewer inserted into the centers of the cakes comes out clean.
Cool for 10 minutes in the pan. Loosen the sides with a small, thin offset spatula. Invert the cake layers, remove the parchment rounds, and transfer the cakes to cooling racks. Cool completely. Level the tops of the cakes with a serrated knife or cake leveler.
Make the caramel frosting: melt the butter in a saucepan over medium-low heat. Add the brown sugar and milk and increase the heat to medium-high. Bring the mixture to a boil and stir until the sugar is completely dissolved. Remove from heat and stir in the salt and vanilla extract. Let the mixture cool until just warm. Pour the mixture into the bowl of an electric mixer and add the powdered sugar; beat until well combined. Immediately fill 2 cake layers each with 1/2 cup caramel frosting and stack them. Transfer the remaining frosting to a large piping bag fitted with a flat cake icer tip (#789) (this caramel frosting has a thick, almost fudge-like consistency, so it’s very difficult to spread – trust me, this decorator tip is the trick!). Pipe the frosting around the edges of the cake and on top in thick overlapping ribbons. When the cake is covered, gently pat the frosting with your fingers until a smooth surface is achieved. The caramel will begin to firm and should not stick to your fingers. This layer of frosting doesn’t have to be perfect; you just want to get a relatively even layer of caramel covering the cake. Refrigerate the cake while you prepare the mocha frosting.
Make the mocha frosting: Cream the butter in an electric mixer fitted with the whisk attachment. Add the powdered sugar and cocoa powder. Mix on low speed until the mixture begins to come together. Add the dissolved coffee and vanilla extract. Mix on medium speed for 1 minute, then increase to high speed and beat until light and fluffy. Scrape the bowl down and beat again until all the ingredients are well incorporated. Remove the caramel-covered cake from the refrigerator and frost the top and sides with the mocha icing using an offset spatula. Transfer the remaining icing to a piping bag fitted with a large star tip. Pipe a few large stars on the top left side of the cake. Dust 3 macarons with the gold luster dust; arrange all of the macarons on top of the piped stars. Scatter flake sea salt on top of the cake (about two to three pinches). Refrigerate the cake until firm.
Decor: While you wait for the cake to chill, roll the chocolate fondant out into two long skinny ropes beneath your palms to about 16 inches long. Twist the two ropes together and lay the piece on a sheet of waxed paper. Using a small artists’ brush, brush gold luster dust over the piece until completely gilded. Remove the cake from the refrigerator and attach the rope around the top edge of the cake with small dots of mocha frosting.
While the cake is still cold and the icing is still firm, use clear acetate to cover the entire upper portion of the cake (secure the plastic with tape), exposing only 1 1/2 inches around the bottom. Brush the exposed area with the luster dust. Remove the plastic.
Allow the cake to come to room temperature before serving.