Cream butter and sugar in large mixer bowl until light and fluffy. Add eggs and vanila; beat well. Combine flour, cocoa, baking soda and salt; gradually blend into creamed mixture. Stir in peanut butter chips. Drop by teaspoonfuls onto ungreased cookie sheet. Bake at 350~F for 8 to 9 minutes. Do not overbake. Cookies will be soft; they will puff during baking and flatten upon cooling.Cool until set, about 1 minute. Remove from cookie sheet; cool completely on wire rack. ----