Preheat oven to 200 degrees.
Line a large baking sheet with aluminum foil and spray generously with non-stick spray. Set aside.
In a large stock pot, add the brown sugar, butter and light corn syrup.
Heat over medium while continuously stirring until it reaches a low boil.
Lower the heat and continue to stir as it boils for 5 minutes.
Remove from heat and add the salt, vanilla and baking soda. Stir as the mixture bubbles and settles.
Add the pretzels 1/3 at a time to the stock pot and stir to coat. This will help to cover all the pretzels.
Pour the pretzels onto the prepared baking sheet and spread out as evenly as possible.
Sprinkle half of the toffee bits over the pretzels.
Bake for 1 hour and 15 minutes stirring and turning the pretzels every 15 minutes.
After baking, remove the pan and sprinkle the remaining toffee bits over the pretzels.
Allow the pretzels to rest for 15 minutes before breaking them apart.