Start by preheating your oven to 350°F (175°C). Line your baking sheets with parchment paper or silicone baking mats to prevent sticking and ensure even baking.
In a large mixing bowl, use an electric mixer to cream together the softened butter, brown sugar, and granulated sugar until the mixture is light, fluffy, and well combined—this usually takes about 3-4 minutes.
Beat in the eggs, one at a time, making sure each is fully incorporated before adding the next. Follow with the vanilla extract, mixing until smooth and fragrant.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt. Gradually add this dry mixture to the wet ingredients, mixing just until combined. Avoid overmixing to keep the cookies tender.
Using a spatula, gently fold in the butterscotch chips, toffee bits, and chopped nuts if using. Be sure to distribute them evenly throughout the dough for maximum flavor in every bite.
Using a cookie scoop or spoon, drop generous mounds of dough onto the prepared baking sheets, spacing them about 2 inches apart to allow for spreading. Bake for 10-12 minutes or until the edges are lightly golden but the centers still look soft.
Remove the cookies from the oven and let them cool on the baking sheets for 5 minutes before transferring them to a cooling rack. This resting time lets the cookies set and develop that signature chewy texture with melty butterscotch puddles.