Mix the crushed biscuits with melted butter until combined, then press into the base of a springform tin. Chill for 30 minutes.
In a large bowl, whisk the cream cheese and icing sugar until smooth.
Add the double cream, lemon zest, lemon juice, and vanilla. Whisk until thick and fluffy.
Spoon the mixture over the chilled biscuit base and smooth the top.
Refrigerate for at least 4 hours, preferably overnight, until set.
Garnish with extra lemon zest before serving.