Chocolate Marble Cheesecake Recipe

Combine crumbs and butter. Grease bottom of 9" springform pan. Press mixture onto bottom. Preheat oven to 300 degrees. In large bowl combine cream cheese, sugar and vanilla. Beat until smooth. Add eggs, one at a time, beating well after each. Set aside 1 cup of mixture. Pour remaining mixture into prepared pan. Fold melted chocolate into the 1 cup cheese mixture. Spoon onto mixture in pan and cut through batter for marble effect. Bake at 300 degrees for 50 to 55 minutes or until just set. Remove to wire rack. Cool completely. Refrigerate 2 hours. Frost top and sides with chocolate sour cream frosting. Refrigerate 4 hours before serving. For frosting, melt chocolate chips in microwave or in top of double boiler. Add sour cream and salt. With wooden spoon beat frosting until creamy and of spreading consistency.