Preheat oven to 325 degrees F (170 degrees C). Lightly grease baking sheets.
Beat butter, sugars, egg, and vanilla at medium speed of electric mixer until fluffy.
At low speed, gradually beat in flour, just until blended. By hand, stir in nuts and chocolate.
Drop by heaping tablespoonfuls, 2 1/2 inches apart, onto lightly greased cookie sheets.
Bake for 17 minutes or until edges of cookies are lightly browned and tops look dry. Allow to cool on baking sheets five minutes, then remove to racks to cool completely.