In a small saucepan, combine water, butter, and chocolate; cook and stir over low heat until smooth. Cool. In a mixing bowl, combine flour, brown sugar, baking soda, and salt. Add eggs and sour cream; beat on low just until combined. Stir in chocolate mixture until smooth.
Preheat the oven to 375 degrees F.
In another bowl, beat cream cheese, sugar, egg, and vanilla; set aside. Spread chocolate batter into a greased 15 by 10 by 1-inch baking pan. Drop cream cheese mixture by tablespoonfuls over batter; cut through the batter with a knife to swirl. Sprinkle with chocolate chips. Bake for 20 to 25 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack.