Prepare the Peach Jam: In a medium saucepan, combine chopped peaches, granulated sugar, cinnamon, and lemon juice over medium heat. Stir frequently for about 10-15 minutes until the peaches soften and the mixture becomes syrupy. In a small bowl, whisk together cornstarch and water to create a slurry, then add it to the peach mixture, stirring until thickened. Remove from heat, let cool, and refrigerate until ready to use.

Make the Streusel Topping: Preheat your oven to 350°F (175°C). In a mixing bowl, combine all-purpose flour, sugars, cinnamon, and a pinch of salt. Cut in the softened unsalted butter until the mixture resembles coarse crumbs. Spread the streusel mixture onto a baking sheet lined with parchment paper and bake for approximately 15-20 minutes, or until golden brown. Set aside to cool.

Prepare the Graham Cracker Crust: In a bowl, mix crushed graham crackers with melted butter and a little sugar until well combined. Press the mixture firmly into the bottom of a springform pan. Bake the crust at 350°F (175°C) for 10 minutes until lightly golden, then remove from the oven and allow it to cool.

Mix the Cheesecake Batter: In a large mixing bowl, beat the cream cheese with granulated sugar until smooth and creamy. Add sour cream and mix until fully incorporated. Gradually add the eggs one at a time, mixing gently. Finally, stir in vanilla extract and a pinch of salt.

Assemble the Cheesecake: Layer the cheesecake batter over the cooled crust. Spoon the prepared peach jam evenly over the cheesecake layer. Sprinkle the cooled streusel topping generously over the peach jam.

Bake in a Water Bath: Wrap the springform pan in aluminum foil to prevent leaks. Place the pan in a larger baking dish and fill it with hot water halfway up the sides. Bake at 325°F (160°C) for 60-75 minutes, or until the edges are set.

Cool and Chill: Once baked, turn off the oven and crack the door open slightly. Let the cheesecake cool for about an hour, then refrigerate for at least 6 hours.

Finish with Whipped Topping: Whip heavy cream and powdered sugar together until soft peaks form. Top the chilled cheesecake with whipped cream and any remaining peach jam.