Preheat oven to 350 degrees. Line a few baking sheets with parchment paper; set aside. In a medium bowl, whisk together flour, baking soda, and salt; set aside.
With an electric mixer, cream butter and sugars until light and
fluffy. Add eggs and vanilla; beat until combined. Add sour cream, and beat until combined. Add flour mixture; beat until just combined. Fold in chocolate and nuts.
Drop dough in mounds (2 level tablespoons each) at least 2 inches
apart onto prepared baking sheets (as you work, chill any remaining dough until ready to bake).
Bake, rotating sheets halfway through, until cookies are golden brown but still soft to the touch, 15 to 16 minutes (chilled dough will take longer). Cool 5 minutes on sheets; transfer to a wire rack to cool completely.