To begin, preheat your oven to 350 and spray two baking pans with non-stick spray.
To a large mixing bowl, add your butter, brown sugar and white sugar and beat together with a mixer till creamy. Add your egg and vanilla and briefly blend in.
To the same bowl, add your flour, cornstarch, baking soda, cinnamon, and salt and stir together till you have a smooth cookie dough. Add your pecans and butterscotch chips and fold them in.
Using a cookie scoop, scoop your dough onto the pans evenly spaced apart (with no more than 12 cookies per pan). Bake in the oven for 10-14 minutes, or till the edges are set but the inside still looks a touch underdone.
Let cool entirely, then devour!
Stored in an airtight container these cookies taste best within 4-5 days.