Favorite Chocolate Marbled Brownies

In small bowl beat cream cheese until smooth, beat in sour cream, sugar, egg, and vanilla to blend thoroughly.
Prepare brownie batter according to package instructions.
Spread half the batter (My note: More than 1/2 the batter must be used or the bottom of the brownie crumbles away when removed from the pan) into greased 9x13 baking pan.
Top with cream cheese mixture, then remaining brownie batter, swirl with knife blade to create marbled effect.
Bake 350F (180C), 40 to 45 minutes until pick comes out clean.
Cool on rack.
Frost.
Chill to set.
Topping: Melt chocolate chips in double boiler, cool slightly, stir in sour cream.
My Notes: I baked these at 325F (160C) for 20 mins.
So watch your cooking time.
Also, use butter to grease the dish and not non-stick spray or the brownie will stick.
13x9x2 inch is not a good size for these, but 9x11 inches is.
Original recipe calls for 6 oz chocolate chips and 3/4 cup sour cream.
Unbalanced.
too heavy on sour cream.
After making this several times using sour cream, I've decided to omit the sour cream and we liked it even better.
I prefer to mircowave chocolate chips instead of using the double boiler.
Go carefully and slowly, stirring often.
You can only tell the chips are melting by stirring.
Frost brownies while frosting is still warm; cut into squares.