Mix together digestive biscuit crumbs and butter then press 25 g (¼ cup) into the bottom of glasses. Chill in fridge whilst you prepare cheesecake filling.
Place marshmallow is a big microwave safe bowl and microwave at 30 second bursts until melted.
Beat together mascarpone cheese, cream cheese and sugar in a bowl until smooth. Stir in melted marshmallow and marshmallow fluff. Mixture may be a little lumpy.
Whip cream in bowl of stand mixer until stiff peaks form and then gently fold into cheese mixture.
Pour filling onto cookie base and smooth over top with spatula. Cover and put in fridge to chill for 4 hours or overnight.