*For Yogurt Cheese: Using a yogurt cheese maker or layered cheese cloth, strain the whey from 1 quart of yogurt for 3-6 hours in the refrigerator. This should yield 1 cup of yogurt cheese.
Mix the graham cracker crumbs and butter together.
Press into the bottom of an ungreased 9-inch springform pan.
Chill.
Preheat oven to 300°.
Cream together cream cheese and sugar.
Add the eggs, vanilla, chocolate and 1 cup of yogurt cheese.
Mix until combined. Spoon into crust.
Place cheesecake on the oven's middle rack with a pan of water on the bottom rack.
Bake for 50 minutes without opening the oven door.
Turn off oven and allow cake to cool for 30 minutes in the oven with the door ajar.
Finish cooling on wire rack.
Refrigerate before serving.