Place the granulated sugar, unsalted butter, and evaporated milk in a medium saucepan.
Set the saucepan over medium heat. Stir continuously while the butter melts and the ingredients combine.
Continue heating and stirring until the mixture reaches a full rolling boil. Confirm that the sugar has dissolved completely and the liquid appears evenly blended.
Remove the saucepan from the heat. Immediately add the quick-cooking oats and dry butterscotch pudding mix.
Stir thoroughly until the oats are completely coated and the pudding powder is distributed uniformly throughout the mixture.
Allow the mixture to rest for several minutes. This brief cooling period will help it begin to thicken.
Add the chopped pecans and toffee bits once the mixture has cooled slightly. Fold them in until they are evenly incorporated and the cookie mixture remains cohesive yet easy to portion.
Cover a cookie sheet with wax paper.
Drop individual spoonfuls of the mixture onto the prepared sheet, leaving enough room between each portion to prevent the cookies from touching.
Leave the cookies at room temperature until they have cooled completely and become firm.