In a large baking pan that has been sprayed with a non stick spray pour pretzels and set aside.
In a sauce pan over low heat place corn syrup, sugars, salt, and butter mix well. When mixture is melted and starts to bubble lightly place lid on pan for 30 seconds. After 30 seconds remove lid and stir with a clean spoon. This action will help prevent any sugar or salt crystals from getting back into the syrup mixture. Turn temperature down and let boil gently for five minutes. Stir frequently while cooking.
When mixture has cooked for 5 minutes remove from heat add baking soda and stir. Make sure all baking soda has been mixed through, the sugar will foam and this normal. Add butter flavoring and stir well.
Pour hot toffee mixture over pretzels. Stir making sure all pretzels are coated.
Place pretzels in a preheated oven at 225 degrees. Every 15 minutes stir pretzels to coat with toffee mixture. Cook these for 60 minutes. When finished baking remove from oven and pour on to a non stick surface. Plastic wrap works well and little mess to clean up.