Prepare the crust: Preheat oven to 325°F (160°C). Mix graham cracker crumbs, sugar, and melted butter. Press into the bottom of a 9-inch springform pan. Bake for 10 minutes, then let cool.
Make the filling: Beat cream cheese and sugar until smooth. Add vanilla, then eggs one at a time, mixing gently. Stir in sour cream and heavy cream until combined. Pour over cooled crust.
Bake the cheesecake: Bake for 50–60 minutes, until the center is almost set. Turn off oven and leave cheesecake inside for 1 hour to prevent cracking. Cool completely.
Prepare the topping: In a small saucepan, combine huckleberries, sugar, and lemon juice. Cook over medium heat until berries release juice. Optional: Mix cornstarch with 1 tbsp water and add to thicken. Cool slightly.
Assemble: Pour huckleberry topping over cooled cheesecake. Refrigerate at least 4 hours, preferably overnight, before serving.