Prepare the springform pan for a water bath. Once the crust has cooled, wrap the springform pan with 2 layers of heavy-duty foil, wrapping and folding the edges at least ¾ up the sides of the pan. For an extra barrier, if desired, place an oven bag around the foil and tie it around the foil to secure it.
Combine the softened cream cheese and sugar in the bowl of a stand mixer with a paddle attachment (or use a hand mixer) and mix on medium until smooth, about 2-3 minutes scraping the sides of the bowl occasionally.
32 ounces (4-8oz packages) cream cheese, 1 cup (200 grams) granulated sugar
Add the eggs one at a time, mixing well after each.
4 large eggs
Add the vanilla and salt and mix well.
2 teaspoons vanilla extract, ½ teaspoons kosher salt
Add the heavy whipping cream and mix until combined.
½ cup heavy whipping cream
Evenly divide the batter between 2 medium bowls.
Melt the bittersweet chocolate in a heatproof bowl in 20 second increments in the microwave, stirring after each time until completely melted.
4 ounces bittersweet chocolate
Melt the white chocolate in another heatproof bowl in the same way.
4 ounces white chocolate
Pour the bittersweet chocolate into one bowl of the cheesecake mixture, mixing well. Pour the melted white chocolate into the other bowl of cheesecake batter and mix well.
Pour the white chocolate cheesecake batter into the prepared pan over the crust. Smooth the top.
Gently spoon (I use an ice cream scoop) the bittersweet chocolate batter over top of the white chocolate batter. Spoon it over the entire batter, trying to cover it completely. Use the back of a spoon or an offset spatula to gently smooth the top and cover the white chocolate layer completely.
Place the springform pan into a roasting pan and place it in the oven. Carefully pour very hot water into the roasting pan until it comes about halfway up the sides of the springform pan being careful not to get any water between the pan and the foil.
Bake the cheesecake at 325 degrees Fahrenheit for 65-75 minutes. If you have an instant-read thermometer, the temperature should be 150-155 degrees Fahrenheit in the middle. The cheesecake is done when the middle is still slightly jiggly but the edges are fully set.
Turn the oven off and slightly prop open the oven door with a wooden spoon if it won’t stay open on its own. Allow to cool in the oven for 1 hour.
Carefully remove the roasting pan from the oven and remove the cheesecake from the water. Remove the foil. Cool for 30 minutes to an hour on a wire rack.
Place the cheesecake in the refrigerator, covering the top with foil or plastic wrap and chill at least 4 hours or overnight.