Mix the cookie crumbs and melted butter until combined, then press down on the bottom of an 8 inch (20 cm) springform cake pan (or line a regular cake pan with plastic wrap). Place in the refrigerator.
In a medium bowl beat together the cream cheese, sugar, zest and juice until creamy. Set aside.
In a large bowl beat the cold cream until stiff peaks appear, set aside
In a small pot add the milk and sprinkle the gelatine on top, let stand one minute, then place the pot on low heat and heat just until the gelatine has dissolved, stirring often (1-2 minutes), do not boil, then immediately remove from heat. Add a heaping tablespoon of the cream cheese mixture to the gelatine mixture and stir gently to combine.
Fold the gelatine into the remaining cream cheese mixture, then gently fold it into the whipped cream, mix until combined.
Remove the cookie base from the fridge, spoon the cheesecake filling evenly on top, cover with plastic wrap and refrigerate 4-5 hours or even better overnight. Before serving top with the blueberry filling if desired.
FOR THE BLUEBERRY TOPPING
In a medium pot mix together the berries, sugar, cornstarch, water and lemon juice. Bring to a boil then lower the heat and simmer until desired thickness. Pour into a clean bowl and refrigerate 1-2 hours. It will thicken as it cools.