For the crust:Preheat oven to 350 degrees. Generously butter an 8 by 8-inch baking dish. Place the crumbs in a large Ziplock bag and mash it with a rolling pin to form crumbs. Pour the crumbs into a large bowl then add in the melted butter. Use a fork to mix until evenly moistened. Press mixture into an even layer in prepared baking dish and bake in preheated oven for 10 minutes. Remove from oven and allow to cool while preparing filling. Reduce oven temperature to 325 degrees.
For the filling:In a mixing bowl, whisk together ¾ cup granulated sugar with the flour. Add cream cheese to mixing bowl and using an electric hand mixer set on low speed, blend together cream cheese and granulated sugar mixture just until smooth, about 1 minute. Add in eggs one at a time and mix just until combined after each addition. Add heavy cream, sour cream and vanilla and blend just until combined. Tap bowl forcefully against countertop about 30 times to release air bubbles. Butter the side of the baking dish and pour filling over crust. Set the 8 by 8-inch baking dish into a 13 by 9-inch baking dish (a roasting pan would be fine too) and pour about 3 cups of hot water into the 13 by 9-inch baking dish.*
Bake in preheated oven until cheesecake is fairly jiggly, about 42 - 45 minutes, then turn oven off and allow cheesecake to rest in warm oven with door closed about 10 minutes longer or until center only slightly jiggles.
Remove from oven and allow to cool on a wire rack at room temperature 1 hour, then cover and chill 4 hours.
For the topping:Cut bars into squares. Sprinkle each square with an even layer of sugar and melt sugar with a culinary torch (it will melt into beads then bubble, then caramelize and turn to a smooth surface).
