In a large microwave-safe bowl, melt 2 cups of chocolate chips and butter; stir until smooth. Combine the sugars, cocoa and coffee; add to chocolate mixture. Stir in eggs and vanilla. Combine the flour, baking powder and salt; gradually add to chocolate mixture and mix well. Stir in the walnuts and remaining chocolate chips.
Drop by rounded teaspoonfuls 2 in. apart onto ungreased baking sheets. Bake at 350° for 10-11 minutes or until edges are set. Remove to wire racks to cool.