To make the blackberry jelly, rinse the blackberries with cold water, gently pat dry with kitchen paper and add them to a pan together with the granulated sugar and lemon juice.
Mix well, then leave them to simmer on a medium heat until they release their liquid and is reduced to a runny jammy texture.
Pass the jam through a sieve to remove all the seeds, then allow the jelly to cool down completely.
To make the biscuit base, add the biscuits to a food processor and blitz to a breadcrumb consistency.
Alternatively, add the biscuits to a ziplock bag, and use a rolling pin to bash them well until you get the right texture.
Add the melted butter and mix well.
Divide the mixture between 12 muffin holes lined with muffin cases.
Use a spoon to press down well for a firm base.
Refrigerate it until ready to use again.
To make the filling, add the cream cheese and mascarpone to a large mixing bowl and use a hand mixer to beat them well.
Add half of the blackberry jelly and beat again for a smooth texture.
Divide the filling between the biscuit bases, then top each of them with the remaining blackberry jelly.
Refrigerate the cheesecakes for at least 4 hours, ideally overnight.