In a large bowl, combine brownie mix, sour cream, melted butter and eggs; mix well. Fold in 1-1/2 cups of the chocolate chips. Spread batter in a buttered 13 x 9-inch baking pan. Bake in a 350°F oven 25 to 28 minutes or until brownies begin to pull away form sides of pan and center is just set (do not over bake.) Transfer pan to wire cooling rack; cool completely. In a food processor or mixer, combine powdered sugar, cream cheese, butter, vanilla and salt; process or mix just until smooth. (Do not over process or frosting will be too soft to spread). Spread frosting over cooled brownies; top with remaining 1/2 cup chocolate chips. Cut into squares. Yield: 24 brownies.