Turn the oven down to 100c fan/120c conventional/250f.
In the bowl of a stand mixer (or use a large bowl with an electric whisk), add the room temperature cream cheese, sugar and flour. Mix to combine.
One at a time, add the eggs, mixing well in between each addition. Then add the sour cream, vanilla and the cooled caramel sauce (about ⅓ cup/90g). Mix until smooth and creamy.
Once incorporated, pour on top of the biscuit base. Gently but firmly, tap the whole cheesecake on the work surface to burst any air bubbles in the cheesecake mix, as this can lead to cracks.
In a different roasting tin or cake tin, add some boiling water and add that to the bottom shelf of the oven to help the cheesecake steam.
Place the cheesecake in the middle of the oven, above the boiling water tin, and bake for 90 minutes.
After 90 minutes, don’t open the door, just turn the oven off and leave to cool completely for 3-4 hours.
Once cool, pour the rest of the salted caramel sauce on top and smooth it out. You don't want the caramel hot here but having it just warmed slightly will help it spread out evenly.
Leave it overnight or at least 4 hours in the fridge.
Once ready to serve, remove it from the fridge for about 20 minutes to lose the fridge chill. Sprinkle with flakey sea salt and serve!