Preheat oven to 350 degrees F (175 degrees C).
In a large bowl, cream together the butter and sugar until smooth.
Beat in the eggs one at a time, then stir in the vanilla.
Combine the flour, cocoa, baking soda and salt; stir into the creamed mixture.
Fold in the white chocolate chips.
Drop by rounded teaspoonfuls onto ungreased cookie sheets.
Bake for 8 to 10 minutes in the preheated oven, until cookies are set.
Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.
