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

Combine chocolate chips and 1/2 cup granulated sugar in double boiler. Heat until chips melt and mix is smooth. Remove from heat and set aside.

In small bowl, combine graham cracker crumbs, 2 tbsp. sugar and melted butter and mix well. Pat firmly into a 9 inch spring form pan or 8x8 pan, covering the bottom and 1 1/2 inch up the sides. Set aside.

In large bowl, beat cream cheese until light and creamy. Gradually beat in 3/4 cup sugar. Mix in sour cream and vanilla. 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 to give marble effect. Bake at 325 degrees for 50 minutes or until only a 2 or 3 inch circle in the center will shake. Cool at room temperature. Refrigerate until ready to serve.