In a medium bowl, whisk together flour, baking soda and salt. Set aside.
In the large bowl of a stand mixer, cream together butter, brown sugar and granulated sugar until light and creamy, about 3-4 minutes.
With the mixer on low speed, add the eggs, one at a time, mixing completely after each addition. Mix in the vanilla extract.
Gradually add the flour mixture, just until combined (do not over-mix). Stir in the butterscotch morsels.
Cover the dough and chill in the refrigerator for at least 1 hour.
Preheat oven to 375° F. Line baking sheets with parchment or silicone mats.
Drop dough by rounded tablespoons two-inches apart on the prepared baking sheets. Place the baking sheets back in the refrigerator or in the freezer for about 10 minutes to chill again.
Bake for 8-10 minutes, or just until light brown around the edges. The centers will still be soft. Let cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.