Preheat oven to 200°F and line a baking sheet with parchment paper.

In a small saucepan, combine brown sugar, butter, and corn syrup. Bring to a boil and cook for 2–3 minutes, stirring constantly.

Remove from heat and stir in vanilla and baking soda until fully combined.

Place pretzels in a large mixing bowl and pour the toffee mixture over them. Stir to coat evenly. Add Heath bits and mix gently.

Spread the coated pretzels onto the prepared baking sheet in a single layer. Bake for 45 minutes, stirring halfway through.

Remove from oven and immediately sprinkle with chopped peanuts. Toss gently to coat.

Let pretzels cool completely. Once cooled, break into pieces and store in an airtight container.