- Pre heat oven to 120°C.
- Lightly spray a 20cm round, 5 cm deep cake tin with non-stick cooking spray and line the base and side with baking paper.
- For the Cheesecake Mixture, put the sugar and salt in the bowl of an electric stand mixer and stir to combine. Add the cream cheese, breaking it into chunks as you put it in the bowl. Using the paddle attachment, mix on speed 2 to slowly cream the mixture, scraping down the side of the bowl often with a flexible plastic spatula.
- With the mixer still on low speed add the eggs scraping well between each addition, then add the sour cream and vanilla paste and mix until combined. Remove the bowl from the mixer and give the mix a final hand whisk to ensure there are no lumps. Add a little of the lemon juice, then taste it before adding a little more, until you reach your tang threshold.
- Pour cheesecake mixture into the prepared cake tin and place the tin in a roasting tin. Pour enough hot water into the roasting tin to come one-third up the side of the cheesecake tin, but don’t allow the tin to start floating. Bake for 45 minutes, or until just springy with no wobble. Remove from the oven and chill for at least 2 hours.
- For the Carrot Cake, turn the oven up to 160°C. Put the hazelnuts on a baking tray and toast until deep golden brown. Cool, then transfer to a sieve and rub the skins off a little, discarding the skins. Chop into a fine crumb. Reserve 20g for decoration.
- Lightly spray two 20cm round x 5cm deep cake tins with cooking oil spray and line the bases and sides with baking paper. Combine the flour, baking powder, bicarb soda, cinnamon and salt in a bowl and set aside.
- Put the egg and sugar in the bowl of an electric stand mixer. With the whisk attachment, whisk on speed 8 for 10 minutes, then reduce to speed 4 and whisk for another 2 minutes. Turn it up to speed 6 and stream in the hazelnut oil.
- Put the grated carrots and nuts in a large mixing bowl and pour the oily foam over them. Gently stir together with a balloon whisk. Sift over the dry ingredients and fold in gently until combined.
- Weigh 520g of batter into each prepared cake tin. Bake for 35 – 40 minutes until the cakes feel fluffy and a skewer comes out clean. Cool the cakes in their tins on a wire rack for 5 minutes, then carefully flip the cakes out and re-invert them so they are top side up.
- For the Frosting, combine all the ingredients in the bowl of an electric stand mixer. Using the paddle attachment, mix on speed 8 (under high) for 10 minutes until fluffy and spreadable.
- To Assemble, once the cake layers are completely cool, lightly shave the tops off both cakes and place one on your serving plate or stand and set it on a cake turntable. Carefully spread a heaped tablespoon of frosting onto the top of each cake and spread it out. Invert the cooled cheesecake directly from the tin onto the bottom cake. Flip the top cake onto the cheesecake, bottom crust side up. If you are a little off centre, use your hands to gently shift the cake top back to perfect alignment
- Swipe around the side of the cake with an offset spatula to smooth out the cheesecake so it is in line with the cake layers. Pile the remaining frosting on top of the cake and smooth it out. Scatter the reserved hazelnuts over the top and serve.