Caramel Swirl Cheesecake

Position a rack in the center of the oven and preheat to 350 degrees F. Place the walnuts in a cake or pie pan and toast for 12 minutes, stirring the pan after 6 minutes. Remove the pan from the oven and cool. Reduce the oven temperature to 300 degrees F.
Spray the inside of the springform pan with nonstick baking spray. Wrap heavy-duty aluminum foil tightly around the bottom of the pan to prevent water from seeping in as it bakes in a water bath.
Pulse the walnuts and brown sugar in the work bowl of a food processor fitted with the steel blade until the walnuts are finely ground, about 1 minute. Pour the butter through the feed tube and pulse until the mixture begins to hold together in moist clumps. Transfer the mixture to the springform pan and press the crust evenly onto the bottom.
Beat the cream cheese in the bowl of an electric stand mixer using the flat beater attachment, or in a large bowl using a hand-held mixer, until fluffy, about 2 minutes. Add the sugars and beat together well. Add the eggs, 1 at a time, beating well after each addition. Add the vanilla then add the sour cream and blend completely.
Pour 1/ 2 of batter into the prepared pan. Then pour 1/ 2 of the caramel sauce over the batter. Use the tip of a knife or a toothpick to swirl together. Repeat once more with the remaining batter and sauce.
Place the springform pan into a larger cake pan or a roasting pan. Pour boiling water into the bottom pan until it comes halfway up the sides of the cake pan. Bake the cake for 1 hour and 30 minutes, or until the cake puffs and the top is light golden. Remove the pans from the oven and transfer the springform pan to a cooling rack to cool completely. Cover the top of the cheesecake with waxed paper and tightly wrap with aluminum foil then chill for at least 8 hours. Release the clip on the side of the springform pan and gently pull the sides away from the bottom.
Serve the cheesecake at room temperature.