In a food processor, blitz the cookies until finely ground, about 1 minute. Pour in the melted butter and blitz again for a few seconds until it all comes together.
Press the mixture into an 11 inch tart pan with a removable bottom and chill in the refrigerator for about 30 minutes.
While the crust is setting mix the mascarpone and custard with an electric mixture until smoothly combined.
Pour into the cold crust and decorate with assorted sliced fruit.
Chill again for another 30 minutes or until firm. Serve immediately from the refrigerator and avoid leaving the tart out too long in warm weather.