Pop your sugar, cream cheese, mascarpone and vanilla extract and into your mixer bowl give it a quick spin to mix it all together. Don't worry about the sugar not dissolving, it will.
In a separate bowl beat your cream until it is stiff. You need to stop beating at the right point because if the cream is too soft so will the cheesecake be, if overbeaten it's hitting the brink of being churned and we don't want butter. It won't take long to beat to the right stiffness so keep an eye on it and regularly stop to check and see if it is ready.
Pop your beaten cream in with your cream cheese mixture and briefly mix it together on a low setting - or fold in by hand. Use your spatula to wipe down the sides and base of the bowl to ensure all of the mixture is equally incorporated.
Take roughly ⅓ of your cheesecake mixture and pop it onto the biscuit base, roughly even out.
Sprinkle over half of your fudge pieces.
Melt your salted caramel sauce in your microwave in bouts of 10 seconds, stirring in-between until it is soft, but not hot. Blob four blobs over the cheesecake mixture, spacing out equally, then take a skewer and drag it through the blobs to create a marbled effect.
Repeat with another layer of cheesecake mixture, caramel and fudge pieces.
Spread over your final layer of cheesecake mixture.
Even out this top layer with your small palette knife, so that it is smooth.
Refrigerate for at least 4 hours, but preferably overnight, ie 12 hours. The longer it has the better it sets.