6 oz. chocolate chips
1/2 c. sugar
1 1/4 c. graham cracker crumbs
2 tbsp. sugar
1/4 c. butter
2 (8 oz.) pkgs. cream cheese
1 tsp. vanilla extract
4 eggs
1/2 c. sour cream

Preheat oven to 325 degrees. Combine over hot (not boiling) water, chocolate chips and 1/2 cup sugar. Heat until morsels melt and mixture is smooth. Remove from heat and set aside.

In small bowl combine graham cracker crumbs, 2 tablespoons sugar and melted butter. Mix well. Pat firmly into 9 inch springform pan covering bottom and 1 1/2 inches up sides.

In large bowl, beat cream cheese until light and creamy. Gradually beat in 3/4 cup sugar. Mix in sour cream and vanilla extract. Add eggs one at a time, beating well after each.

Divide batter in half. Stir melted chocolate mixture into first half. Pour into crumb lined pan. Cover with plain batter. With knife, swirl batter with chocolate batter to marbelize. Bake at 325 degrees for 50 minutes or until only a 2-3 inch circle in center will shake. Cool at room temperature. Refrigerate.