I highly recommend preparing the components the day before, and assembling them the night before you need them to allow the cake to freeze overnight. Remove from the freezer three hours before you serve to allow time to defrost

BROWN BUTTER CAKE

1. Preheat the oven to 350f/180c. Spray a half sheet baking tray (18 x 13 inches) with baking spray.
2. Brown the butter by melting over medium heat, then continuing to cook until light brown and nutty smelling. Remove from heat and allow to cool.
3. In the bowl of a stand mixer fitted with the paddle attachment, combine the butter, brown butter and sugars. Beat on high for approximately 5 minutes, until fluffy. Add the eggs one at a time, mixing well after each addition, and scraping the bowl down as needed. Mix for 2-3 minutes until homogenous. 
4. With the mixer on low, slowly add the buttermilk, oil and vanilla. Mix on medium for approximately 10 minutes, until the mixture has come together uniformly. This step may take up to 15 minutes. Scrape the bowl down well. 
5. Add the flour, baking powder and salt, and mix until just combined, scraping the bowl down well and mixing for another 20 seconds to ensure even distribution of the dry ingredients. 
6. Spread the mixture into the sheet pan, and smooth with a spoon or spatula. Bake for 30 to 35 minutes, checking for doneness after 30 minutes. The cake will be golden brown and the edges will spring back when lightly touched. Ensure that the middle is not jiggly. 
7. Remove from the oven and cool completely. Cover with plastic wrap until ready to use. 

CHEESECAKE FILLING

1. Preheat the oven to 300f/150c
2. In the bowl of a mixer fitted with the paddle attachment, mix the cream cheese on medium speed for 3 minutes, until smooth. Add the sugar and mix until well combined, scraping down the bowl well. 
3. In a small bowl, measure out the corn starch and salt. Slowly whisk the milk into the corn starch, ensuring that there are no lumps. Add the eggs and mix well. With the mixer running, slowly add the milk and egg mixture to the cream cheese. Mix for 5 minutes until smooth. 
4. Spread into a glass oven dish or loaf pan, and bake for 15 minutes, or until the outside edges of the cheesecake are just firm, and the centre is still jiggly. Continue to cook in 5 minute increments if it is not yet at that stage. Remove from the oven and cool, then use an immersion blender or blender to blend the mix until homogenous and uniform in texture. Store in the fridge until ready to use. 

PIE CRUMB

1. Preheat the oven to 350f/180c. Line a baking tray with silpat or parchment paper. 
2. In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, sugar and salt until well mixed. Add the butter and water and mix on low until clustered. 
3. Spread the mixture on the tray, and bake for 25 minutes, until golden brown. Break up into smaller clumps during the baking process. Remove from the oven and allow to cool (it will firm up a lot during cooling). Store in an airtight container until ready to use

APPLE PIE FILLING

1. Fill a bowl with water, and juice the lemon into it. 
2. Peel, core and quarter the apples. Dice each quarter into small pieces (cut into quarters lengthways, then each quarter into quarters, leaving you with 16 pieces per quarter). Transfer apple to the bowl of lemon water as you go. 
3. Drain the apples, and add to a medium pan. Add the brown sugar, butter, cinnamon and salt, and cook on medium heat, stirring occasionally, for 3-5 minutes. The apples will release liquid and begin to cook down. When the apples are fork tender, remove from the cooking liquid with a slotted spoon. Cool and refrigerate until ready to use. Make the cake soak with the remaining cooking liquid.

CAKE SOAK

1. Using the liquid left from the apple, heat over medium heat. Cook for 5 minutes, swirling the pan often, until the mixture has reduced and thickened slightly. Add apple cider and mix until incorporated. Alternatively you can skip the reducing step and use the liquid as is, omitting the apple cider. 

PIE CRUMB BUTTERCREAM

1. Add milk and pie crumb to a blender. Mix on high for 2-3 minutes, until a smooth paste consistency is reached. 
2. In the bowl of a stand mixer, mix the butter and icing sugar on high until smooth and pale. Scrape down the sides, and add the pie crumb paste. mix well on high for 2-3 minutes, scraping down the bowl as needed, until the frosting is pale and uniform. If the consistency is too runny, add more icing sugar as needed, and mix well. 
3. Transfer to an airtight container and store in the fridge until ready to use. 

ASSEMBLY

1. Using the cake ring or a three inch cookie cutter, cut circles from the sheet pan. You need 18 in total (six cakes at three layers each). You may not get 18 full circles cut out, but you can use scraps pushed together to form the bottom layers of some of the cakes to make up the total cake layers to 18.
2. On a lined sheet pan, line six 3 inch cake rings with acetate, so the acetate forms cylinders that extend out of the cake rings. It needs to be about five inches high if you are using sheets, otherwise you will need two strips of acetate (you put the second sheet on when you are about halfway through stacking)

LAYER ONE

1. Place a circle of cake in the bottom of each cake ring, pushing down to make sure it is sitting flat. If you need to make up cake circle numbers now is the time - push scraps into the bottom of the rings to form the bottom layer. 
2. Using a pastry brush or spoon, gently brush or spoon over some of the cake soak, until the top of the cake layer is moist.
3. Divide half of the liquid cheesecake between the rings. Use the back of a spoon to smooth it down.
4. Sprinkle a layer of pie crumb over the cheesecake filling, pressing down well with your hands to ensure that they are in place.
5. Divide half of the pie filling between the cakes. 

LAYER TWO

1. Repeat the same process as layer one. 

LAYER THREE

1. Finish off each cake with the final cake circle. Spread the top of each cake with the pie crumb frosting, and decorate with extra pie crumbs. 
2. Freeze the cakes for at least 12 hours, to allow all of the filling layers to set. Three hours before you are ready to serve, remove them from the freezer, pop them out of the cake rings, and carefully peel away the acetate layers to reveal the cake inside. Transfer to a serving platter, and allow to defrost before serving.
3. Leftovers can be wrapped in plastic, and frozen or kept in the fridge.