Preheat the oven to 150°C.
Grease a 20cm springform cake tin with butter and line the base with greaseproof paper.
Mix the crushed biscuits and melted butter in a bowl.
Press the mixture into the tin and chill in the fridge for 20 minutes.
Whisk ricotta, double cream, eggs, sugar, and flour in a separate bowl.
Fold the raspberries into the mixture.
Pour the filling over the chilled base and bake for 85 minutes or until set.
Cool the cheesecake and remove it from the tin.
Heat raspberries in a pan over low heat until puréed.
Strain the purée through a sieve to remove seeds.
Simmer cream in a separate pan and stir in chocolate pieces until melted.
Stir in the raspberry purée, strain through a fine sieve, and keep warm.
Serve a slice of cheesecake with sauce and a scoop of ice cream.