- Combine crumbs, sugar, and margarine; press onto bottom of 9-inch Spring- form cake pan.
- Bake at 350 degrees F., 10 minutes.
- Combine cream cheese, sugar and vanilla, beating at medium speed on electric mixer until well blended.
- Add eggs, one at a time, mixing well after each addition.
- Blend chocolate into 1 cup batter.
- Spoon plain and chocolate batters alternately over crust; cutting through batters with knife several times for the marble effect.
- Bake at 450 degrees F., 10 minutes.
- Reduce oven temperature to 250 degrees F.; continue baking 30 additional minutes.
- Loosen cake from rim of pan; cool before removing rim of pan.