* The 1 oz square of unsweetened Chocolate should be melted. ~- ~- 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. Chill.