1/2 c. semi-sweet chocolate chips
1/4 c. butter, softened
3 lg. eggs
1/2 c. sour cream
Powdered sugar
1 c. chocolate cookie crumbs
4 (8 oz.) pkgs. cream cheese, softened
3/4 c. sugar
1 tsp. vanilla

Heat oven to 350 degrees. Stir chocolate chips in small saucepan over low heat until melted and smooth. Remove from heat; set aside. Mix cookie crumbs and butter in 8 inch spring-form pan with fork until thoroughly combined. Press firmly and evenly over bottom of pan. Set crust aside. Beat cream cheese, eggs, sugar, sour cream, and vanilla in large bowl on medium speed until smooth. Remove half of batter to second bowl. Stir in chocolate; blend well. Spoon plain and chocolate batters alternately into prepared pan; marble. Bake 1 hour. Turn oven off; leave cake in oven 30 minutes. Cool cake in pan. Remove sides of pan; sprinkle with powdered sugar.