Heat oven to 200°F and cover a baking sheet with foil. Place a cooling rack over the pan, and spray the rack with nonstick cooking spray. Set aside.
Working quickly, pour the pretzels into the toffee mixture and stir. Transfer the pretzels, a few at a time (with a toothpick or fork) to the prepared cooling rack/baking tray, laying them side-by-side without touching.
Bake at 200°F for 20-30 minutes to dry out the pretzels and to ensure they won't be sticky. Transfer the pretzels to a cooling rack to completely cool.
Once the toffee pretzels have cooled. Allow the pretzels to sit uncovered, overnight, on the counter. Keep in an airtight jar or bowl.
A candy thermometer is necessary for making this recipe.