Beat butter and sugar in large bowl until creamy. Add eggs and vanilla; beat until light and fluffy. Stir together flour, cocoa, baking soda and salt; gradually beat into butter mixture. Stir in white chips. Drop by rounded teaspoons onto ungreased cookie sheet.
Bake 8 to 9 minutes. (Do not overbake; cookies will be soft. They will puff while baking; flatten upon cooling.) Cool slightly; remove from cookie sheet to wire rack. Cool completely.