Grease bottom of 23 cm Springform pan. Prepare basic brownie mix asdirected on package; pour batter evenly into springform pan. Bake at350 degrees F., 15 minutes.
Combine cream cheese, sugar and vanilla, mixing at medium speed on electricmixer until well blended. Add eggs, one at a time, mixing well after eachaddition. Pour over brownie layer. Spoon chocolate over cream cheesemixture, cut through cheese and chocolate mixture several time to acheivea marble effect. Bake at 180ºC ., 35 minutes. Loosen cake from rimof pan; cool before removing rim of pan. Chill. Garnish with whippedcream, if desired.