Prepare brownie mix according to box instructions. Pour into a greased, 9" spring-form pan. Bake for 15 minutes.
Cheesecake
Beat cream cheese in a stand mixer until light and fluffy. Add sugar, flour, sour cream, and vanilla. Mix to combine. Add eggs and beat until the mixture is smooth and all the ingredients are incorporated. Scrape the sides and the beater as needed. Pour the batter over the brownie layer after the brownie layer has baked for 15 minutes.
Place on the middle rack of the oven. Add a pan, partially-filled with water, under the cheesecake. This "water-bath" allows the cheesecake to bake without cracking. Bake for one hour, or until the cheesecake is no longer jiggly in the center. Cook longer as necessary, checking every five minutes, until done.
Remove the cheesecake from the oven, and allow it to come to room temperature on the counter.
Huckleberry Topping
Combine sugar and cornstarch in a saucepan. Add water and stir until smooth. Add the huckleberries and lemon juice then bring to a boil. Cook and stir for a few minutes or until thickened. Set aside to cool.
Once cool, add the huckleberry topping over the cheesecake and chill for 4 or more hours before serving.
Notes
For high altitude, add an additional ¼ cup of flour and 2 tablespoons of water to the brownie mix before baking.
If you don't have a 9" springform pan, a 10" may be used.
Although I always use a water bath when I bake a cheesecake, you can skip it since the huckleberry topping will cover up any cracks that develop.
Store huckleberry cheesecake in an airtight container in the fridge for up to a week.