Preheat your oven to 350°F (175°C) and prepare a 9x13 inch baking pan by greasing it or lining with parchment paper.

In a large mixing bowl, beat together the softened unsalted butter, light brown sugar, and granulated sugar on medium speed for about 3 to 5 minutes until light and fluffy.

Add the large eggs one at a time, mixing well after each addition, then stir in the vanilla extract until fully combined.

In a separate bowl, whisk together the all-purpose flour, baking soda, and salt, then set aside.

Gradually add the dry ingredients to the wet mixture, stirring slowly until just combined.

Fold in the butterscotch chips evenly throughout the batter.

Pour the batter into the prepared baking pan and spread evenly. Bake for 20 to 25 minutes until golden brown and a toothpick comes out with a few moist crumbs.

Allow the bars to cool completely in the pan for about 30 minutes before slicing into squares.