In a mixing bowl, whisk together caster sugar, cornflour, and a pinch of salt until evenly combined.
Add the cream cheese and beat on medium speed for 2–4 minutes until the mixture is smooth and the sugar is fully dissolved (you can rub a bit between your fingers to check for graininess).
Add the egg and vanilla extract, and whisk again until fully incorporated.
Slowly pour in the liquid whipping cream while mixing on low speed. Mix just until combined—avoid overmixing to reduce air bubbles in the batter, which could cause the cheesecake to crack. Tap the bowl a few times to help release any trapped air.
Pour half the cheesecake mixture over the cooled crust and smooth the surface.
Gently place the frozen carrot halwa layer over the cheesecake batter and press down lightly to settle it in. Pour the remaining cheesecake mixture on top and spread it evenly with an offset spatula.
Place the cheesecake on the middle oven rack, and place a tray filled with boiling water on the bottom rack to create steam and prevent cracking.
Bake the cheesecake undisturbed for 1 hour. After that, continue baking until the edges are firm and the center still jiggles slightly. This may take another 15-30 minutes. Avoid overbaking—it will continue to cook as it cools in the oven.
Once done, turn the oven off and leave the cheesecake inside with the door closed for another hour. This gradual cooling process helps prevent the top from cracking. Let it cool on the counter for another hour, then refrigerate for at least 6 hours or overnight to fully set.
Remove the cheesecake from the pan, top with the cooled salted caramel, and serve cold.