Preheat your oven to 375 degrees F and line a baking sheet with foil, parchment paper, or a silicone baking mat.
Arrange 4 cups of the pretzels in a single layer over the bottom of the baking sheet, then set aside.
In a saucepan over medium heat, combine the butter and brown sugar. Bring the mixture to a boil, then continue boiling for 3 minutes, stirring continuously.
Remove the hot butter and brown sugar mixture from the heat and stir in the vanilla extract, then pour the toffee mixture evenly over the pretzels.
Bake for 5-7 minutes. It should be bubbling all over.
In a microwave safe bowl, combine your chocolate chips of choice with vegetable oil. Microwave in 30 second intervals, stirring in-between, until melted and smooth, then spread the melted chocolate on top of the Pretzel Toffee.
Immediately sprinkle with any desired toppings, then let the toffee and chocolate set completely. Break into pieces and store in an airtight container (put wax paper or parchment between layers) for up to 2 weeks!