Butter the base and sides of a 23cm cake tin. Then melt butter in a bowl. Pulse the biscuits in a food processor and then add to the melted butter. Put in to the cake tin and press it firmly into place. Leave in fridge whilst preparing rest of dessert.
Put the mascarpone into a bowl and beat until soft. Melt the fudge in a microwave and let cool down slightly. Then whisk the cream and stand to one side.
Add the fudge to the mascarpone and mix until fudge blends well, don’t worry about small lumps of fudge as these add to the consistency, although remove any large bits that don’t blend in. Gently fold in the cream and then poor over the biscuit base. Place in a fridge for 4-6 hours until it sets well.
For the sorbet put all the ingredients into a food processor and blend until smooth consistency. Check for sweetness and if necessary add a bit more sugar.
Place in a container and into the freezer, after about an hour remove and give it a good stir and replace in the freezer. Before serving you can put it back in the food processor or give it a good mix before you serve it up with a slice of the sticky fudge cheesecake.