In large bowl, cream butter and sugar with an electric mixer until light and fluffy. Add in eggs and vanilla; beat well.
In separate bowl, whisk together flour, cocoa, baking soda and salt. Blend into creamed mixture just until combined. Stir in both types of chips.
Drop by tablespoonfuls onto ungreased cookie sheets. Bake for 10 to 11 minutes, or until slightly set. Do not overbake! Cookies will be soft, and will puff while baking and flatten while cooling. Cool slightly and then remove from cookie sheet to rack.