First make your Mojito flavoured syrup. Place your lime zest, lime juice, mint and sugar into your saucepan and heat gently, whilst stirring constantly, until the sugar granules have disappeared.
Simmer gently for 1 minute then set aside to cool.
Strain the liquid using a tea strainer or fine mesh sieve and discard the strainer contents.
Mix your white rum into your cooled syrup.
Place your cream cheese and mascarpone into your mixer bowl and mix on a medium-low setting until combined. 15 seconds or so should do it.
Gradually pour in ¾ of your cooled syrup and mix on a medium-high setting until just combined. Place the remainder of your syrup in your fridge, covered, until you are ready to serve.
Using your hand or stand mixer, beat your double (heavy) cream until it forms stiff peaks. Be careful not to over beat so that it doesn't become grainy.
Tip your cream into your cream cheese and mascarpone mixture and fold in gently using your spatula until totally combined.
Tip all of the mixture onto your chilled biscuit base and spread out with the back of a dessert spoon. Wipe the sides of the tin clean so that you have a clean edge.
To create a pattern, pop your cheesecake onto a lazy susan (turn table), take a teaspoon and insert just the tip of the handle into the cheesecake topping to a depth of about 3mm only. Then move the lazy susan around so that the tip of the handle creates a circular groove through the cheesecake. You will find a build up will occur on a regular basis so just wipe this off an continue.
Refrigerate for 4 hours minimum or preferably overnight.
Remove from the tin by taking a butter knife and sliding this around the edge of the cheesecake. Then push up from the base to release it from the tin.