Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a medium bowl, combine the flour, cornstarch, and salt. Mix well and set aside.
In a larger bowl, cream together the softened butter and powdered sugar using an electric mixer. Add the vanilla extract and mix until well blended.
Gradually add the dry ingredients to the butter mixture, stirring until fully incorporated. Fold in the butterscotch chips and toffee bits.
Place a sheet of plastic wrap on a countertop or work surface. Transfer the dough onto the plastic wrap and shape it into a log approximately 2.5 inches in diameter. Wrap the dough tightly in the plastic wrap and chill in the refrigerator for 1 to 2 hours.
After chilling, unwrap the dough and slice it into approximately ¼-inch thick pieces. Arrange the slices on the prepared baking sheet, spacing them at least 2 inches apart.
Bake in the preheated oven for 10 to 12 minutes or until the edges are lightly browned. Remove from the oven and let the cookies cool on the sheet for 2 minutes before transferring them to a wire rack to cool completely.
Once cooled, serve these delectable Butterscotch Shortbread Cookies and enjoy every bite!