400g/14oz fresh raspberries
1 tsp vanilla extract
150²µ/5Β½΄Η³ϊ digestive biscuits
200g/7oz white chocolate, broken into chunks
75²µ/2ΒΎ΄Η³ϊ butter, plus extra for greasing
300ml/10fl oz double cream
250g/9oz mascarpone cheese