Cream butter or margarine and sugar in large mixer bowl. Add eggs and vanilla; blend well. Combine flour, cocoa, baking soda and salt; gradually blend into creamed mixture. Stir in nuts, if desired. Drop by teaspoonfuls onto un- greased cookie sheet. Bake at 350 for 8 to 9 minutes. (Do not overbake. Cookies will be soft. They will puff during baking, flatten upon cooling.) Cool on cookie sheet until set, about 1 minute; remove to wire rack to cool completely.
