Polka Dot Cheesecake

From http://bakersdaughter.typepad.com/

¼ cup cocoa

2 tbsp sugar
1 cup Graham crumbs

¼ cup melted butter....
Filling

16 oz softened cream cheese

½ cup sugar

2 eggs

2 oz dark chocolate, melted 

1 tsp vanilla

2/3 cup sour cream

• Preheat oven to 300 degrees F.
• Grease a 7 X 7 inch square pan and line it with parchment paper.
• In a small bowl, mix together the graham crumbs, sugar, cocoa, and melted butter and press into the pan.
• Beat cream cheese until smooth.  Gradually add the sugar.  Scrape down the sides of the bowl.  Add the eggs one at a time on low speed.  Add vanilla and sour cream.  Scrape the sides of the bowl one more time and beat until smooth.  Reserve 1/2 cup of the cheesecake filling and set aside.
• Melt the 2 oz of dark chocolate in a bain marie (a bowl placed over a pot of barely simmering water), or in a microwave on low temperature.  Stir the melted chocolate into the reserved 1/2 cup of cream cheese filling.  
• Pour the plain batter into the pan, smoothing out to the edges.  To make the dots you will need a pastry bag fitted with a round tip.  Fill the pastry bag with the chocolate cheesecake mixture.  Gently press the tip of the bag into the smoothed out plain cheesecake and squeeze the bag forming a dot.  Place dots all over the cheesecake until the chocolate mixture is used up.  
• Place in the oven and bake for 1 hour.  Turn off the oven and leave the cheesecake in the oven for an additional 1 hr.  Refrigerate for at least 24 hours.   Freeze if you wish for about 1/2 hour before cutting.  Use a knife dipped in hot water to help when cutting.