1 (8 oz.) pkg. (1 c.) semi sweet chocolate chips
1/2 c. sugar
1 1/4 c. graham cracker crumbs
2 tbsp. sugar
1/4 c. butter, melted
2 (8 oz.) pkgs. cream cheese
3/4 c. sugar
1/2 c. sour cream
1 tsp. vanilla extract
4 eggs

Preheat oven to 325 degrees. Combine in double boiler, chocolate chips and 1/4 cup sugar; heat until melted and the mixture is smooth. Remove from heat and set aside.

In a small mixing bowl, combine graham cracker crumbs, 2 tablespoons sugar and melted butter. Mix well. Pat firmly into 8" springform pan, covering bottom and 1 1/2" up sides. Set aside.

In large bowl, beat cream cheese until light and creamy. Gradually beat in 3/4 cup of sugar. Mix in sour cream and vanilla extract. Add eggs, one at a time. Divide batter in half. Stir melted chocolate into first half and pour into crumb lined pan. Cover with plain batter and swirl with knife to marbelize.

Bake at 325 degrees for 50 minutes or until only a 2 to 3 inch circle in center will shake. Cool and refrigerate.