01 - Preheat oven to 325°F. Grease a 9-inch springform pan with butter and line the bottom with parchment paper. Wrap the outside of the pan with 2-3 layers of aluminum foil to prevent water from seeping in during the water bath.
02 - Combine crushed graham crackers, melted butter, brown sugar, and cinnamon in a medium bowl until the mixture resembles wet sand. Press firmly and evenly into the bottom of the prepared pan using the back of a measuring cup or spoon.
03 - Bake the crust for 10 minutes until lightly golden and set. Remove from oven and place on a wire rack to cool while preparing the filling.
04 - Using a stand mixer or hand mixer on medium-low speed, beat the softened cream cheese and granulated sugar together until completely smooth and creamy, about 2-3 minutes. Scrape down the sides and bottom of the bowl to ensure no lumps remain.
05 - Add the pumpkin purée, sour cream, and vanilla extract to the cream cheese mixture. Beat on medium speed until well incorporated, about 1 minute. Scrape down the bowl again.
06 - Add the flour, pumpkin pie spice, and salt. Mix on low speed until combined. Add eggs one at a time, beating on low speed just until each egg disappears into the batter. Do not overmix.
07 - Pour the filling over the cooled crust. Tap the pan gently against the counter 2-3 times to release any air bubbles. Place the springform pan inside a large roasting pan and pour boiling water into the roasting pan until it reaches halfway up the sides of the cheesecake pan.
08 - Carefully transfer to the oven. Bake for 50-60 minutes until the edges are set and puffy but the center still jiggles slightly like gelatin when gently shaken. The center should not be liquid.
09 - Turn off the oven and crack the door open about 2 inches. Let the cheesecake cool in the oven for 1 hour. This gentle cooling helps prevent cracking.
10 - Remove the cheesecake from the water bath and remove the foil. Run a thin knife around the edge to loosen it from the pan. Cool completely at room temperature for 1 hour, then refrigerate for at least 4 hours or overnight until completely cold and firm.
11 - Just before serving, whip the cold heavy cream, powdered sugar, and vanilla extract on medium-high speed until soft peaks form. Do not overwhip or the cream will become grainy.
12 - Release the springform ring and run a knife under the bottom to loosen. Transfer to a serving plate. Spread or pipe the whipped cream over the chilled cheesecake. Dust with ground cinnamon if desired. Slice with a sharp knife dipped in hot water, wiping the knife clean between slices.