1 cup (2 sticks) unsalted butter, room temperature
1 cup packed light brown sugar
1 pkg. (12 oz.) OR 2 cups semisweet chocolate chips
Mix flour, baking soda and salt in medium bowl.
Beat butter, brown sugar and granulated sugar in mixer bowl on medium speed until light and fluffy, about 3 minutes. Add eggs and vanilla; beat on low speed until blended. Gradually add flour mixture, beating just until blended. Stir in chocolate chips and walnuts.
Refrigerate, covered, until firm, about 1 hour or overnight.
Heat oven to 375°F. Drop dough by tablespoonfuls, 2 inches apart, onto parchment paper-lined or ungreased baking sheets.
Bake in 375°F oven until lightly browned, 9 to 11 minutes. Cool on baking sheets 1 minute. Remove to wire racks; cool completely.