Preheat oven to 375°F. In a medium bowl, whisk together flour, baking soda, and salt. Set aside.
In a large bowl, beat the softened butter and both sugars together until light and fluffy, about 3 minutes.
Add eggs one at a time, beating well after each addition. Mix in the vanilla extract.
Gradually stir in the flour mixture until just combined. Don't overmix!
Fold in the butterscotch chips and pecans (if using).
Drop rounded tablespoons of dough onto ungreased cookie sheets, spacing them about 2 inches apart.
Bake for 10-12 minutes until edges are golden brown. Let cool on the baking sheet for 2 minutes before moving to a wire rack.