Preheat oven to 325 0F
In a small bowl, combine crumbs and butter. Mix well. Press into bottom of a 8 inc springform pan. Wrap outside of pan with heavy-duty foil. Set aside.
In a large mixing bowl, using an electric mixer set on medium speed, beat cream cheese and sugar for 2 minutes. Beat in sour cream, flour, and vanilla. Add the eggs, one at a time, beating well after each addition.
Transfer 1 1/2 cups of batter to a small bowl. Stir in chocolate. Spread half of vanilla batter over crust. Top with half of chocolate batter. Spoon remaining vanilla batter over chocolate batter. Top with remaining chocolate batter.
Using a knife, gently swirl batters together. Place pan in a shallow roasting pan; add enough boiling water to come half way up sides of springform pan. Bake until just set, about 1 hour 15 minutes.
Place pan on a wire rack and cool to room temperature.
Cover and chill for 4 hours.
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