Prepare the Crust:

• Preheat your oven to 325°F (165°C).
• In a mixing bowl, combine graham cracker crumbs, granulated sugar, and melted butter.
• Press the mixture into the bottom of a 9-inch springform pan.
• Bake for 10 minutes. Remove and let it cool.

Make the Filling:

• In a large mixing bowl, beat the cream cheese until smooth.
• Add sugar and vanilla extract, continuing to beat until well combined.
• Beat in the eggs one at a time.
• Mix in sour cream, heavy cream, orange zest, and orange juice until smooth.
• Pour the filling over the cooled crust.

Bake the Cheesecake:

• Wrap the bottom of the springform pan in aluminum foil to prevent leaks.
• Place the pan in a larger baking pan and fill the outer pan with hot water halfway up the sides of the springform pan (water bath).
• Bake for 55-65 minutes until the center is set but still slightly wobbly.
• Turn off the oven and let the cheesecake sit in the oven for 1 hour.
• Remove from oven and refrigerate for at least 4 hours or overnight.

Prepare the Topping:

• In a small saucepan, combine orange marmalade, cornstarch, and water.
• Cook over medium heat, stirring constantly until thickened.
• Cool slightly before spreading over the chilled cheesecake.

Serve:

• Remove cheesecake from springform pan.
• Garnish with whipped cream and orange slices.
• Slice and serve chilled.