Pre-heat the oven to 300°F and line a baking sheet with parchment paper.
In a saucepan, over medium heat, melt the butter, brown sugar and corn syrup.
Let it simmer for 3 to 4 minutes until it becomes bubbly.
Remove the saucepan from the heat and stir in the vanilla extract.
Place the pretzels in a medium bowl; pour the toffee mixture over the pretzels; toss to coat evenly with the toffee.
Spread the coated pretzels on the prepared baking sheet, in a single layer, and sprinkle with peanut butter chips.
Place in the pre-heated oven and bake for 10 – 12 minutes.
Remove from the oven and immediately sprinkle with sea salt flakes.
Allow the pretzels to cool completely to harden before breaking them apart and serving.
