Whisk together the flour, baking soda, and salt in a medium bowl. Set aside.
Cream together butter, white sugar, and brown sugar in a large bowl with an electric mixer on medium speed until light and fluffy (about 2-3 minutes). Add egg and vanilla; beat well. Gradually add the flour mixture just until combined, being careful not to over-mix. Gently fold in the nuts and fruit.
Chill the dough for about 1 hour.
Preheat the oven to 375°F.
Using a 1 ½-tablespoon cookie dough scoop, drop the batter about 2 inches apart on parchment-lined baking sheets.
Bake for 9-11 minutes, or just until lightly browned on the edges but still soft in the centers.
Allow the cookies to cool on the cookie sheets for a few minutes, and then transfer them to wire racks to cool completely.