To make the filling place the blackberries and sugar into a saucepan. Cook with the lid on over a low heat for 10 minutes or until stewed and broken down. Use a potato masher to break everything up then pass through a fine sieve and into a clean bowl. Squeeze the water out of the gelatine and add to the bowl of berries, mixing until everything is dissolved and smooth. Leave to cool.
To make the pastry case melt the butter over a low heat in a small saucepan. Brush the cake tin with some melted butter then one by one brush the filo sheets, pressing into the cake tin to line the bottom and the sides. Press against the edge of the tin well with each new sheet so they still well together. Using scissors trim the top so it’s neat, then line with greaseproof paper and fill with baking beans. Bake for 25 minutes, then remove the beans and return to the oven for a further 5-10 minutes until the base is golden brown. Remove from the oven and leave to cool.
In a food processor whizz the cream cheese with the cream until smooth then add the pureed fruit and continue to whizz until fully incorporated. Tip into the pastry case, smooth the top then set aside in the fridge to set for a minimum of 4 hours, preferable overnight.
Once ready to serve, decorate with extra blackberries, physalis and crushed pistachios.