Place the softened butter and powdered sugar in a large mixing bowl. Beat for about 2–3 minutes, until the mixture becomes smooth, light, and creamy.
Pour in the vanilla extract and mix until it is evenly incorporated into the butter mixture.
In a separate bowl, whisk together the all-purpose flour and salt until evenly combined.
Gradually add the flour mixture to the butter mixture. Mix on low speed just until a soft dough forms. Avoid mixing longer than necessary, as overmixing can make the cookies less tender.
Gently fold the butterscotch baking chips into the dough using a spatula. Continue folding until the chips are distributed throughout the dough.
Shape the dough into a log approximately 2 inches in diameter, or flatten it into a thick disc. Wrap it securely and refrigerate for 30 minutes.
Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
Remove the chilled dough from the refrigerator and cut it into rounds about ¼ inch thick. Arrange the cookies on the prepared baking sheets, leaving approximately 2 inches between each cookie.
If desired, lightly sprinkle the tops of the cookies with coarse sugar for a subtle crunchy finish.
Bake for 12–15 minutes, or until the edges are just beginning to turn a light golden brown. The centers should remain relatively pale.
Allow the cookies to cool on the baking sheets for 5 minutes. Then carefully transfer them to a wire rack and let them cool completely before serving.
