1. Heat oven to 350°F. Line 8-inch square baking pan with foil; grease foil. Prepare CREAM CHEESE MARBLE; set aside.
2. Stir together flour, baking soda and salt. Combine sugar, butter and water in medium saucepan. Cook over low heat, stirring constantly, until mixture comes to a boil. Remove from heat; immediately add 1 cup chocolate chips, stirring until melted. Stir in eggs and vanilla until blended; gradually add flour mixture, blending well. Spread 2/3 of chocolate batter into prepared pan.
3. Spoon CREAM CHEESE MARBLE over chocolate; drop spoonfuls of remaining chocolate batter onto cream cheese. Gently swirl chocolate batter into cream cheese with spatula.
4. Bake 35 to 40 minutes or until brownies begin to pull away from sides of pan. Cool completely in pan on wire rack. Remove from pan; peel off foil. Cut into squares. About 18 brownies.
CREAM CHEESE MARBLE: Beat 1 package (3 oz.) softened cream cheese and 1/4 cup sugar in small bowl until smooth. Add 1 egg and 1/2 teaspoon vanilla extract; beat well. Stir in remaining 2/3 cup chocolate chips.
MINT VARIATION: Substitute 1-2/3 cups (10-oz.pkg.) HERSHEY'S Mint Chocolate Chips . Add 2 drops green food color to CREAM CHEESE MARBLE, if desired.