Heat oven to 160C/fan 140C/gas 2. Put the gluten/dairy free biscuits into a plastic bag, seal tightly and bash with a rolling pin until you have fine crumbs.
Tip into a bowl and mix in the melted lactose free butter.
Spoon the crumbs into the base of a 23cm springform tin and press down with the back of a spoon. Bake for 10-15 mins until lightly browned, then cool.
Put all of the filling ingredients in a large bowl and beat until smooth. Pour onto the cooled biscuit base and return to the oven for 50 mins to 1 hr until the filling is just set and starting to brown.
Leave the cheesecake to cool in the oven with the door slightly open, then chill in the fridge. If the top has cracked it doesn’t matter.
Can be made up to 2 days ahead. Carefully remove from tin and transfer onto a serving plate.
Mix the passion fruit pulp and icing sugar until it has dissolved. Spread over the top of the cheesecake, then serve.