Preheat the oven to 350 degrees Fahrenheit and line the bottom of a 9-inch springform pan with parchment paper.
Lay 4 sheets of foil on a work surface in a cross/star pattern. Place the pan in the center and wrap the foil tightly on all sides, ensuring there are no tears. Secure it at least halfway up the side of the pan but not over the rim at the top. Set aside.
In a medium bowl, mix the graham cracker crumbs with the sugar and melted butter. Stir until all the crumbs are moist, then pour them into the prepared springform pan. Use a measuring cup to press the crumbs evenly into the bottom and about 3/4 of the way up the sides.
Bake the crust for 8 minutes or until golden brown. Remove from the oven and set aside to cool. Then, increase the oven temperature to 400 degrees Fahrenheit (200°C).
In a separate large mixing bowl, beat the cream cheese until smooth and lump-free with an electric mixer. Scrape the sides and bottom of the bowl with a spatula and beat again for 1 minute.
Add the sugar and cornstarch and beat on medium speed until smooth and fluffy, about 2 minutes. Scrape the sides of the bowl as needed.
Add the eggs and egg yolk and beat on low until well blended. Finally, add the sour cream, heavy cream, and vanilla and stir with a spatula until just combined.
For the water bath: boil about 6 cups of water. Place the springform pan with the baked crust into a larger pan or roasting dish. Pour the filling over the crust, then place the two pans into the oven. Before closing the door, pour the hot water into the outer pan, around the springform pan. It should reach about halfway up the side of the springform pan.
Bake for 10 minutes, then reduce the heat to 230 degrees Fahrenheit (110°C) and continue baking for 1 hour. Do not open the door.
After 1 hour, turn the oven off and open the door a few inches. Do not open it all the way. Leave the cheesecake to cool for 1 hour in the residual heat. After an hour of cooling in the oven, take the cheesecake out and leave to cool fully on the counter. Then, place it in the fridge for at least 8 hours – overnight is best.
While the cheesecake cools, make the strawberry sauce. In a medium saucepan, combine half of the sliced strawberries with the sugar, lemon juice, and cornstarch. Turn the heat to medium and cook until the sugar dissolves and the sauce has thickened. Stir constantly to keep it from burning. Then, remove the pot from the heat, stir in the remaining fruit, and leave to cool. Finally, transfer to an airtight container and keep in the fridge until ready to use.
When the cheesecake is fully set, remove it from the springform pan and place on a serving plate. Stir the strawberry sauce and spread it over the top. Serve with fresh whipped cream, and enjoy!
