Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper.
Cream together the butter, light brown sugar, and granulated sugar until smooth.
Beat in the vanilla extract and scrape the bowl down to ensure even mixing.
In a separate bowl, whisk together the flour, baking soda, and salt. Gradually blend into the wet mixture.
Stir in the butterscotch chips until evenly distributed.
Drop tablespoon-sized balls of dough onto the lined baking sheet, spacing them about 2 inches apart.
Bake for 10–12 minutes until edges are lightly browned and centers are set but still soft.
Let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.
Notes
Store cooled cookies in an airtight container at room temperature for up to 4 days. For longer storage, freeze in a sealed container for up to 3 months.