Heat oven to 325°F. Wrap a 9-inch springform pan with heavy foil and lightly grease the inside.
Stir graham crumbs, 2 tbsp sugar, and 1/2 tsp cinnamon. Mix in melted butter until evenly moistened.
Press crust into the pan bottom and slightly up the sides. Bake 8 minutes, then cool while you make filling.
Beat cream cheese on medium until smooth and fluffy, about 2 minutes. Scrape the bowl.
Add brown sugar and 1/4 cup granulated sugar. Beat until creamy and no lumps remain; scrape again.
Mix in pumpkin puree, sour cream, and heavy cream on low until blended.
Whisk eggs in a small bowl. With mixer on low, slowly stream in eggs just until combined.
Blend in vanilla, pumpkin pie spice, extra cinnamon, salt, and flour. Tap bowl to release air bubbles.
Pour batter over the crust. Set the pan in a roasting pan and pour hot water around it, about 1 inch deep.
Bake 55–65 minutes until edges are set and the center wobbles slightly. Turn off oven; crack door and rest 1 hour.
Remove from water bath. Run a thin knife around the edge; cool to room temperature.
Chill covered at least 6 hours or overnight. Slice with a warm, dry knife and top with whipped cream.