Preheat your oven to 350 degrees. Get out your 9-inch springform pan. Put the crumbs, Splenda blend and margarine in the pan. Mix with a fork until the butter is completely mixed into the crumbs and the Splenda sort of disappears into the mixture. Pat this mixture with your fingers into the bottom of the pan and partially up the sides of the pan. It should come up the side a half inch or more. You don't have to be too precise. Bake for 8 to 9 minutes until set. Let cool.
To make the Filling:
First drain the sweet potatoes in a colander. Put the sweet potatoes in a food processor and whiz them to make a puree. You can add up to a half cup of water to make the potato puree smooth. Sometimes you need a little liquid to get the processor started in its chopping process.
In a large bowl, put in your cream cheese, Splenda blend, sweet potato puree mixture, spice, and one egg. Mix for one minute, stopping the mixer to scrape down the sides. Add the next egg and mix another minute. Add the last egg and the vanilla and mix one more minute. This makes your filling nice and fluffy. Pour this over your crust. Level it with your spatula
Wrap your cheesecake pan in two layers of aluminum foil. You want to seal it good and tight so no water will get in. Wrap the bottom and up the sides. Set the pan in a larger roasting pan and then add water so the water level will be one inch up the side of the cheesecake. Bake at 350 degrees for 1 hour and 45 minutes until the cheesecake is set. Remove the cheesecake from the water pan and put it back in the oven (now turned off) with the door open for 15 more minutes so the cheesecake cools down slowly. Then let it cool on the counter. Take off the aluminum foil side cover. Finally, chill the cheesecake in the refrigerator overnight before serving. You can put a loose covering of plastic wrap on top of the cheesecake after it has cooled on the counter so it doesn't soak up any refrigerator flavors.
To make Whipped Cream:
Whip your cream as usual. Instead of adding vanilla or sugar when the cream reaches soft peaks, add the syrup and continue beating until stiff peaks form. Make the whipped cream right before you serve.
Take a sharp knife and slide it along the edge of the cheesecake to make sure it is loosened from the pan edge. Place it on your platter and unlock the springform to release the cheesecake. Gently lift off the outer ring. Clean up any little crumbs or messy edges. Slice your cheesecake with a very sharp knife that has been dipped in warm water and wiped off with a towel. This will make a very smooth cut.
The cheesecake will taste best on days 2 through 4. As the days progress, the cheesecake flavor intensifies. Depending on the humidity in your refrigerator, your crust might start to get soggy, but the cheesecake will still taste good. As with all cheesecakes, I recommend taking it out of the refrigerator at least 15 to 30 minutes or even longer before you serve it. The colder it is, the less the flavors come through. Savor each bite by rolling it over on your tongue. Yum!