Preheat oven to 350. Prepare browni mix as directed. Spread in a well greased 9x13x2 pan.
In large bowl beat cream cheese, butter and cornstarch until fluffy. Gradually beat in the Eagle Brand. Add egg and vanilla, beat well. Pour over brownie batter.
Bake 40-45 minutes, or until top is lightly browned. Spread with frosting if desired. Cut into bars. Store covered in refrigerator.