Increase the oven to 350°F. Bring 4 to 6 cups of water to a boil (enough to halfway fill a large roasting pan) and set aside. Place a large roasting pan on the very bottom rack of your oven. Place a second rack just above the roasting pan.
Meanwhile, place the cream cheese in the bowl of an electric mixer. Using the paddle attachment, mix the cream cheese on medium-low for 4 to 5 minutes, or until completely smooth. Stop and scrape down the bowl every couple of minutes.
Add the sugar and salt into the cream cheese and mix for another 3 to 4 minutes. Stop the mixer and scrape down the bowl. Mix for another 30 to 60 seconds to smooth out any lumps.
With the mixer on low, add in the Amarula Cream Liqueur, eggs, and egg yolk. Allow each egg to fully incorporate into the batter before add in the next. Stop the mixer and scrape down the bowl.
Add the sour cream. Mix on lo speed for a couple of minutes or until the batter is creamy and uniform.
Pour the batter into the prepared crust. Smooth out the top as needed. Rap the bottom of the cake pan on top of the counter a few times to expel any trapped air bubbles. Wrap the sides of the pan in a double layer of foil.
Very carefully pour the hot water into the roasting pan (pouring the water into the pan while it is already in the oven may be easier than trying to carry and place a pan full of boiling water into the oven). Place the baking pan on the rack above the roasting pan and bake for 1 hour. When done, the sides should be puffed and set while the center 2 to 3 inches should jiggle when the pan is moved. If it is not ready, check again after an additional 10 minutes of baking. Once done, turn the oven off and prop the door open with a wooden spoon. Allow the cake to cool inside the humid oven for about 30 minutes.
Once cool, removed the cake from the oven and place on a wire rack. Turn the oven back on to 350°F. As the oven heats back up, combined the sour cream, sugar, and Amarula Cream Liqueur for the topping (recipe to follow). Carefully spread the sour cream topping over the top of the cheesecake with a small offset spatula. When the oven is ready, return the cake pan back to the oven and bake for 10 minutes.
Let the cheesecake cool for an additional 30 minutes on a wire rack, then place in the refrigerator. Drape a piece of parchment paper over the top of the cheesecake to prevent condensation from forming and chill for at least 4 hours, or overnight.
To unmold the cheesecake, carefully run a think knife around the edges of the cake before unlocking the spring-form pan. Warm a metal spatula under hot water, dry, the run it around the edges of the cheesecake to smooth. Top with the cooled Amarula Caramel Sauce (recipe to follow) before serving.