1. Heat oven to 350°F. Cut chocolate into 1/2-inch pieces; set aside.
2. Beat butter, brown sugar, granulated sugar and vanilla in large mixer bowl until thoroughly blended. Beat in eggs, one at a time, beating well after each addition.
3. Stir together flour, baking soda and salt. Gradually beat into butter mixture. Stir in chocolate pieces and nuts, if desired. Drop by slightly rounded tablespoonfuls 2 inches apart on ungreased cookie sheet.
4. Bake 11 to 13 minutes or until toasty brown. Cool 5 minutes on cookie sheet; remove to wire rack. Cool completely. Makes about 5-1/2 dozen cookies.