Reduce Champagne

1. Add the champagne to a medium sized saucepan and cook over medium heat. Allow the mixture to come to a boil, stirring occasionally, until it has reduced to 3/4 cup, about 10-15 minutes. To measure, pour the champagne into a measuring cup. If it’s more than 3/4 cup, add it back to the pan and continue to cook it.
2. Pour the champagne reduction back into the measuring cup and set aside or refrigerate until it reaches room temperature.

Make the Crust

1. Preheat oven to 325°F (163°C). Line a 9-inch (23cm) springform pan with parchment paper in the bottom and grease the sides.
2. Combine the crust ingredients in a small bowl. Press the mixture into the bottom and up the sides of the springform pan.
3. Bake the crust for 10 minutes, then set aside to cool.
4. Cover the outsides of the pan with aluminum foil so that water from the water bath cannot get in (see how I prepare my pan for a water bath). Set prepared pan aside.

Assemble and Bake

1. Reduce oven temperature to 300°F (148°C).
2. In a large bowl, beat the cream cheese, sugar and flour on low speed until well combined and smooth. Be sure to use low speed to reduce the amount of air added to the batter, which can cause cracks. Scrape down the sides of the bowl.
3. Add the sour cream and vanilla extract and mix on low speed until well combined.
4. Add the cooled champagne reduction and mix on low speed until well combined and smooth. 
5. Add the eggs one at a time, mixing slowly to combine after each addition. Scrape down the sides of the bowl as needed to make sure everything is well combined.
6. Pour the cheesecake batter into the crust.
7. Place the springform pan inside another larger pan. Fill the outside pan with enough warm water to go about halfway up the sides of the springform pan. The water should not go above the top edge of the aluminum foil on the springform pan.
8. Bake for 1 hour 5 minutes. The center should be set, but still jiggly (how to tell when your cheesecake is done baking). 
9. Turn off the oven and leave the door closed for 30 minutes. The cheesecake will continue to cook, but slowly begin to cool as well.
10. Crack the door of the oven for 30 minutes to allow the cheesecake to continue to cool slowly. This process helps prevent cracking.
11. Remove the cheesecake from the oven and set aside to cool to about room temperature. Letting it cool to room temperature before refrigerating it can help reduce condensation formation on top. Once at room temperature, remove water bath wrapping and refrigerate until firm, 5-6 hours or overnight. (see note below about when to add topping to the cheesecake)

Topping

1. Remove the cheesecake from the springform pan and place on a serving platter.
2. To make the champagne topping, combine the cornstarch, sugar and salt in a saucepan. Whisk together until there are no more lumps of cornstarch.
3. Add the champagne, cream and butter and stir together to combine.
4. Cook over medium heat (not higher) until it begins to boil, then let it boil for one minute (don’t let it boil longer or the cornstarch can break down). It should be thick and pudding-like. 
5. Remove from heat and spread evenly over the top of the cheesecake.
6. Place cheesecake back into the fridge to cool for at least 1 hour. 

Whipped Cream

1. Add the whipped cream, powdered sugar and vanilla extract to a large mixer bowl and whip on high speed until stiff peaks form.
2. Pipe shells of whipped cream around the outer edge of the cheesecake. I used Ateco tip 847. Decorate with sprinkles, if desired.