1 cup graham cracker crumbs
3 tablespoons granulated sugar
3 tablespoons margarine, melted
24 ounces cream cheese, softened
3/4 cup granulated sugar
1 teaspoon vanilla extract
3 eggs
1 (1 ounce) square unsweetened chocolate, melted

Combine crumbs, the 3 tablespoons sugar and margarine; press onto bottom of a 9-inch springform pan. Bake at 350 degrees F for 10 minutes.

Combine cream cheese, the 3/4 cup sugar and vanilla extract, mixing at medium speed of 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; cut through batters with a knife several times for marble effect. Bake at 450 degrees F for 10 minutes. Reduce oven temperature to 250 degrees F, then continue baking for 30 minutes. Loosen cake from rim of pan; cool before removing rim of pan. Chill.