Preheat the oven to 360 degrees F. Spray a quarter sheet pan and line it with parchment and spray again. Set aside.
In a stand mixer fitted with the paddle attachment, combine the flour, sugar, cocoa powder, baking powder, baking soda and salt. Mix for about 30 seconds.
In a separate bowl, combine all of the wet ingredients and whisk for a few seconds.
With the mixer on low speed, slowly add the wet ingredients to the dry ingredients. Once all the wet ingredients are added, continue to mix on low speed for 30 seconds. Scrape down the sides of the bowl and mix for another 15 to 30 seconds. Don't over beat this batter.
Pour the batter into a quarter sheet baking pan. Bake the cake for 16-18 minutes.
FOR THE SHORTBREAD BUTTERCREAM
Combine the shortbread cookie crumbs, milk, and salt in a blender. Turn the speed to medium-high and puree until smooth and homogenous. This should take about 1 to 3 minutes, depending on your blender (I use a Magic Bullet). If the mixture does not catch on your blender blade, turn the blender off, take a small teaspoon, and scrape down the sides of the canister, remembering to scrape under the blade, then try again.
In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and powdered sugar, and beat together on medium-high for 2 to 3 minutes, until light and fluffy. Scrape down the sides of the bowl with a spatula and mix for another 20 seconds.
On low speed, add the contents of the blender to the butter and powdered sugar. After 1 minute, crank the speed up to medium-high and let the mixture beat for another 2 minutes. Scrape down the sides of the bowl. If the mixture is not a uniform, very pale, barely tan in color, give the bowl another scrape-down and another minute of high-speed paddling.
Use the frosting immediately, or store it in an airtight container in the fridge for up to 1 week.
FOR THE GANACHE
In a microwave safe bowl, heat the cream for about 1 minute. Pour the cream over the chocolate and let sit for about 5 minutes. Mix the chocolate and cream until smooth and shiny. If needed, microwave the mixture for an additional 30 seconds.
Let cool slight before adding to the cake.
FOR THE SHORTBREAD CRUMBS
Preheat your oven to 350 degrees F. Line a baking sheet with parchment paper. Set aside.
Combine the sugar and butter in the bowl of a stand mixer fitted with the paddle attachment. Stir in the flour. If the mixture is too crumbly, you can add another tablespoon of butter.
Sprinkle the shortbread cookie dough crumbs evenly over the baking sheet.
Bake for about 20 minutes, until lightly golden brown on top. Cool completely before using.
FOR THE COCONUT FILLING
Mix sugar, water and corn syrup in a small saucepan.
Bring the water and sugar mixture to boil over medium heat, but DO NOT STIR. (Stirring encourages crystallization). Let the mixture cook until it caramelizes into a golden brown color. It happens quickly, so keep an eye on it.
Remove the caramelized sugar syrup from the heat and slowly mix in the cream. Pour in just a tiny bit at a time, especially at the beginning, and mix to combine. You can start adding more and more as you go along.
Mix in salt and vanilla. Stir to combine.
Set the caramel sauce to the side and let cool while you toast the coconut.
Set your oven to 425 degrees F. Line a baking sheet with parchment and pour all of the coconut evenly onto the baking sheet. Bake the coconut for about 10 minutes, or until golden brown. Remove from oven and toss, and then toast for another 10 minutes, or until golden brown all over. Let cool completely.
Combine the caramel and the coconut. You'll use about 1/3 of the mixture for each layer of the cake.
For the cake, put a piece of parchment or a silpat on the counter. Invert the cake onto it and peel off the parchment or silpat from the bottom of the cake. Use the cake ring to stamp out 2 circles from the cake. These two full circles will be your top 2 cake layers. The remaining cake “scraps” will come together to make the bottom layer of the cake.
You can see pictures from the Milk Bar website HERE or check my Instagram and YouTube for videos.
For the first layer, clean the cake ring and place it in the center of a sheet pan lined with clean parchment. Line the cake ring with one strip of acetate.
Place the cake scraps together inside the ring and use the back of your hand to tamp the scraps together into a flat even layer.
Use the back of a spoon to spread one-third of the chocolate ganache in an even layer over the cake.
Sprinkle about 1/3 of the shortbread cookie crumbs evenly over the ganache. Use the back of your hand to anchor them in place.
Use a piping bag to pipe about 1 cup of the shortbread cookie frosting into the shortbread cookie crumbs.
Sprinkle 1/3 of the toasted coconut caramel filling over the frosting.
For the second layer, gently tuck the second strip of acetate between the cake ring and the top ¼ inch of the first strip of acetate, so that you have a clear ring of acetate 5 to 6 inches tall – high enough to support the height of the finished cake.
Set a cake round on top of the coconut filling, and repeat the process for layer 1 (if 1 of your 2 cake rounds is jankier than the other, use it here in the middle and save the prettier one for the top).
For the third layer, nestle the remaining cake round into the coconut filling, cover the top of the cake with the remaining ganache, shortbread cookies, shortbread frosting and coconut filling.
Transfer the sheet pan to the freezer and freeze for a minimum of 12 hours to set the cake and filling. The cake will keep in the freezer for up to 2 weeks (make sure to wrap in plastic wrap).
At least 5 hours before you are ready to serve the cake, pull the sheet pan out of the freezer and, using your fingers and thumbs, pop the cake out of the cake ring. gently peel off the acetate, and transfer the cake to a platter or cake stand. Let it defrost in the fridge for a minimum of 4 hours (wrapped well in plastic, the cake can be refrigerated for up to 5 days).