Crust

1. Preheat the oven to 350ºF. Grease the springform pan and wrap the outside of the pan in foil. Set aside. 
2. In a bowl, mix crushed graham crackers, butter and sugar. Transfer to the pan and press evenly into the bottom using the bottom of a glass. Place the crust in the oven and bake for 10 minutes until the crust is slightly brown around the edges. Remove from oven and let it cool. 

Cheesecake Filling

1. In a bowl, mix the cream cheese, sugar, cornstarch and salt until combined and creamy. Stir in sour cream and vanilla then mix until combined. Add one egg at a time and stir to combine. Make sure to scrape the sides of the bowl and mix until smooth, creamy and silky.  
2. Into another bowl, pour 1 cup of the cheesecake batter and mix with the dulce de leche. Make sure it is all well combined. Set aside.  
3. Pour the remaining cheesecake batter over the cooled crust then add a few dollops of the dulce de leche mixture over the cheesecake batter. Using a knife, gently make about 3-4 swirls to give a marble effect. Save any leftover dulce de leche mixture to frost the cheesecake once cool. 
4. Transfer the springform pan to the middle of a large roasting pan. Carefully fill the roasting pan with about an inch of hot water. This will help the cheesecake remain creamy without cracks. Bake the cheesecake for 55-60 minutes.  
5. Remove cheesecake from oven. The cheesecake is done when the outer rim looks set but the middle jiggles when you gently shake the pan. Let the cheesecake cool completely on a cooling rack. This step is crucial for achieving the perfect cheesecake.  
6. Frost the cheesecake with remaining dulce de leche, if desired, then place in the refrigerator for at least 4 hours or up to 72 hours.