Step 1: Prepare Your Oven and Pan
Preheat your oven to 325°F (163°C). Wrap the outside of a 9-inch springform pan completely with aluminum foil (at least two layers) to prevent water from seeping in during the water bath. Grease the inside of the pan lightly with butter or cooking spray.

Step 2: Make the Graham Cracker Crust
In a food processor, pulse graham crackers until they become fine crumbs, or place them in a sealed plastic bag and crush with a rolling pin. Transfer crumbs to a medium bowl and mix with sugar, melted butter, and salt until the mixture resembles wet sand and holds together when pressed. Press the mixture firmly into the bottom of your prepared springform pan, using the bottom of a measuring cup to create an even, compact layer. Bake the crust for 10 minutes, then remove and let cool while you prepare the filling.

Step 3: Beat the Cream Cheese
In a large mixing bowl, beat the softened cream cheese on medium speed for 3-4 minutes until completely smooth, light, and fluffy with no lumps. Scrape down the sides and bottom of the bowl frequently to ensure everything is evenly mixed.

Step 4: Add Sugar and Sour Cream
Add the sugar and beat for another 2 minutes until well combined. Add the sour cream and mix on low speed just until incorporated. Don’t overmix at this stage.

Step 5: Incorporate Eggs Carefully
Add the eggs one at a time, mixing on low speed after each addition just until the yellow disappears. Overmixing after adding eggs can incorporate too much air, which leads to cracks. Scrape down the bowl between each egg.

Step 6: Add Final Ingredients
Pour in the heavy cream, vanilla extract, cornstarch (if using), and salt. Mix on the lowest speed just until everything is combined and smooth. The batter should be thick, creamy, and lump-free.

Step 7: Pour and Smooth
Pour the filling over the cooled crust. Tap the pan gently on the counter a few times to release any air bubbles. Use a spatula to smooth the top into an even layer.

Step 8: Prepare the Water Bath
Place the wrapped springform pan inside a larger roasting pan. Carefully pour hot water into the roasting pan until it reaches about halfway up the sides of the springform pan. The water bath ensures gentle, even cooking and helps prevent cracks.

Step 9: Bake Low and Slow
Bake at 325°F for 1 hour and 30 minutes. The cheesecake is done when the edges are set but the center still has a slight jiggle (about a 2-inch circle in the middle). It should not be liquid or soupy, just slightly wobbly—it will firm up as it cools.

Step 10: Cool Gradually
Turn off the oven and crack the door open about 4 inches. Let the cheesecake cool in the oven for 1 hour. This gradual temperature change prevents sudden contraction that causes cracks.

Step 11: Finish Cooling
Remove the cheesecake from the water bath and remove the foil. Run a thin knife around the edge to loosen it from the pan (this prevents cracking as it cools). Let it cool completely at room temperature for another hour.

Step 12: Refrigerate
Cover the cheesecake with plastic wrap (don’t let it touch the surface) or aluminum foil and refrigerate for at least 6-8 hours, preferably overnight. This chilling time is essential for the texture to set properly.

Step 13: Serve and Enjoy
When ready to serve, run a knife around the edge again and carefully remove the springform pan sides. Slice with a hot, clean knife (dip in hot water and wipe between cuts) for perfect, clean slices.