1Preheat oven to 325°, grease bottom and sides of spring form pan, wrap bottom of pan with a double layer foil, and place into a roasting/cake pan. Begin boiling a large pot of water.
2Combine vanilla wafers and melted butter, and then press into the bottom and up the sides of the spring form pan. You can refrigerate this while making the filling.
3In the bowl of stand mixer begin mixing the cream cheese on low until smooth scraping down the sides and the paddle, gradually add the sugar and mix for about 2 minutes until creamy, add the eggs one at a time making sure they are fully incorporated, and finally mix in the vanilla and sour cream.
4In a small bowl heat the Dulce de Leche in the microwave for a bout 1 to 1 1/2 minute, until slightly fluid and easy to work with.
5Spread 1/2 cream cheese mixture over the crust, then spread about 3/4 of the Dulce de Leche on top of the cream cheese mixture making sure to smooth with a spatula, then spread remaining cream cheese mixture on top of the Dulce de Leche smoothing with a spatula, and then placed dollops of remaining Dulce de Leche and use the tip of the knife to make swirls through the top of the cheesecake.
6Place the roasting pan, with a springform pan in it, on the center rack of the oven, and carefully pour the boiling water into the roasting pan until it is about halfway up the sides of the springform pan. Reduce the oven temperature to 300° and bake for 80 minutes. The center will still be slightly jiggly, but will set up as it cools. DO NOT open the oven while baking or test the center of the cheesecake to check for doneness!!
7Once removed from the oven run a thin spatula between the sides of the pan and the cheesecake. Let cool for about 30 to 45 minutes and then refrigerate loosely covered for about 5 hours, and then removed the springform pan.