Combine flour, cocoa, baking soda and salt in a bowl.
Beat sugar and butter with an electric mixer in a large bowl until smooth and creamy. Add eggs one at a time, beating well after each addition. Stir in vanilla. Gradually mix in dry ingredients, then fold in white chocolate chips. Drop by spoons full onto ungreased baking sheets.
Bake 8 to 10 minutes. Remove from oven and let cool on baking sheets for 5 minutes, then transfer to a wire rack to cool completely.
