Vanilla-Chocolate Swirl Cheesecake

20 Oreo Chocolate Sandwich Cookies,
     crushed
3 T butter, melted
4 pkg (8-oz each) cream cheese, softened
1 c granulated sugar
1 t vanilla extract
1 c sour cream
4 eggs
6 squares semi-sweet chocolate, melted

Preheat oven to 325 degrees. Line a 13x9-inch baking pan with foil, letting the ends extend over the sides of the pan. Combine cookie crumbs and butter. Press firmly into the bottom of prepared pan. Bake at 325 degrees for 10 minutes. In large mixer bowl, beat cream cheese, sugar and vanilla with an electric mixer on medium speed. Add sour cream and mix well. Add eggs, one at a time, beating on low speed after each addition, until blended. Set aside one cup of batter. Stir melted chocolate into remaining batter and pour over crust. Top with spoonfuls of remaining 1 cup of plain batter. Cut through batters with a knife several times to swirl. Bake at 325 degrees for 40 minutes or until center is almost set. Cool completely, then refrigerate for 4 hours or overnight. Lift cheesecake from pan using foil handles. Cut into squares to serve. Refrigerate leftovers. Makes 16 servings.