In a bowl, mix graham cracker crumbs, sugar, and melted butter until evenly combined. Press firmly into the bottom of a 9-inch (23 cm) springform pan to form an even crust (you can use a rolling pin to press it in more firmly). Refrigerate while preparing the filling.
In a large mixing bowl, beat cream cheese, mascarpone, and powdered sugar until smooth and creamy (make sure there are no lumps). Mix in vanilla extract and lemon juice.
In a separate bowl, whip cold heavy cream until soft peaks form.
Gently fold the whipped cream into the mascarpone and cream cheese mixture until smooth and fluffy.
Spread the mascarpone filling evenly over the chilled crust and smooth the top with a rubber spatula. Refrigerate for at least 4 hours until fully set.
In a small saucepan, combine blueberries, sugar, and lemon juice. Cook over medium heat until berries begin to release their juices.
In a small bowl or dish, mix cornstarch and water to make a slurry.
Stir into the berries and cook 2 - 3 minutes until the compote thickens and becomes glossy.
Let the compote cool completely, then spoon it over the chilled cheesecake before serving. Add some decorations, such as fresh berries and edible flowers, for a good visual appeal.