Heat oven to 375°F. In large bowl, beat brown sugar and butter with electric mixer on medium speed until light and fluffy, or mix with spoon. Beat in vanilla and egg white.
Stir in flour, cocoa, baking soda and salt. Stir in chocolate chips. Onto ungreased cookie sheet, drop dough by teaspoonfuls about 2 inches apart.
Bake 8 to 9 minutes or until set (do not overbake). Cool 1 minute; remove from cookie sheet to wire rack.