Brownie Chocolate Chip Cheesecake

1 package brownie mix
3 (8 oz.) pkgs cream cheese, softened
1 (14 oz.) can sweetened condensed milk
3 eggs
2 tsp vanilla
1/2 C chocolate chips

Preheat oven to 350.  Grease bottom only of a 9 inch springform pan.  Prepare brownie mix as package directs for chewy brownies.  Spread evenly in prepared pan.  Bake for 30-35 minutes or until set.  In a large mixing bowl, beat cream cheese until fluffy.  Gradually beat in sweetened condensed milk.  Add eggs and vanilla; mix well.  Place the chocolate chips in a small baggie, along with 1 T flour, and shake to coat.  Stir in chocolate chips into the cream cheese mixture.  Pour on top of hot brownie layer.  Reduce oven temperature to 300 degrees.  Bake for 50 minutes or until set.  Turn off oven, leave cheesecake in the oven, and leave the oven door open while it cools (cooling slowly like this will prevent it from cracking).  Chill thoroughly.  Remove the side of springform pan.  Garnish as desired.  Store leftovers covered in the refrigerator.