Place cookies/crackers in the bowl of a food processor and process into fine crumbs. Pour in the melted butter and blend until the mixture resembles wet sand.
Line a muffin pan with paper liners and add a few spoonfuls of crumbs into the base of each liner. Press down and flatten with the back of a spoon and set aside.
To make the filling, combine room temperature cream cheese, mascarpone, condensed milk and lemon juice in a bowl and whip with electric beaters for 2 minutes or until thick and smooth.
Beat in the passion fruit (you can strain out the seeds if you prefer). Fill each liner with cheesecake mixture and add a swirl of passion fruit to the top of each cheesecake (optional).
Allow the cheesecakes to set in the fridge for at least 12 hours but ideally overnight.