1. Heat oven to 350°F. Grease 13x9x2-inch baking pan.
2. Stir together cocoa and baking soda in large bowl; stir in 1/3 cup butter. Add boiling water; stir until mixture thickens. Stir in sugar, eggs and remaining 1/3 cup butter; stir until smooth. Add flour, vanilla and salt; blend completely. Stir in chocolate chips. Pour into prepared pan.
3. Bake 35 to 40 minutes or until brownies begin to pull away from sides of pan. Cool completely in pan on wire rack. Frost if desired. Cut into squares. Makes 24 to 36 brownies.