Bring all cold ingredients to room temperature. With an electric mixer, combine the cream cheese and sweetener at slow to medium speed, scraping sides often. Add all other ingredients except eggs, pumpkin, and chocolate. When completely mixed (with no lumps), add the eggs and egg yolk, one at a time, beating very slowly. When eggs are incorporated separate out one cup of batter then fold pumpkin into the rest of the batter. When pumpkin is blended, do not mix any more. Over-mixing the eggs is a contributing cause of cracked cheesecakes. (The leading cause of cracking is over-cooking, so don't believe any one who tells you it is normal for a cheesecake to be cracked; it isn't.) Always treat the batter gently.

To the one cup of separated batter, add the melted white chocolate and blend.

Add half of the pumpkin batter to a well greased springform pan. Add spoonfuls of the white chocolate batter, and then cover with remaining pumpkin batter. Swirl through with spatula to create marbling effect.

Place the pan on a very large piece of aluminum foil, and fold the foil up around the pan to create a watertight barrier around the cheesecake. Then place the springform pan in an even larger pan and fill the larger pan halfway with water. This is called a water bath. It is a gentler way to cook the cheesecake.

Place the entire water bath containing the cheesecake in a 300-degree preheated oven. Cook for 1 hour and reduce heat to 200 degrees for 1 more hour. Turn oven off and leave cheesecake in until the oven is completely cool. The cheesecake can even be left overnight at this point. Cracks can also occur when a cheesecake cools too quickly, so don't rush this process. Let it set up for several hours in the fridge, preferably overnight.

Garnish with curls of white chocolate.

If you don't want to add the chocolate, just keep all the batter together and make the entire cake pumpkin, it will work fine that way too.