Preheat an oven to 180 degrees C. In a small bowl, combine crushed biscuits, sugar and melted butter. Press mixture evenly into the bottom of a pie pan. Bake for 8 minutes, and remove from oven. When cool, break into small pieces.
Combine buttermilk, sweetened condensed milk, cream cheese, lemon juice, zest and salt in a blender or food processor. Process until smooth. Pour into an ice cream maker and freeze according to the manufacturer's instructions.
Mix in cashews and pieces of the cheesecake base. Gently fold in the jam to create a ribbon effect. Transfer to the freezer for 1 hour to harden.