Preheat your oven to 400°F (200°C).
Spread the pretzels in a single layer on a baking sheet.
In a saucepan, melt the butter over medium heat.
Add brown sugar, salt, and vanilla to the melted butter.
Bring the mixture to a boil, stirring constantly for about 3-5 minutes.
Remove the saucepan from heat and immediately pour the toffee over the pretzels.
Use a spatula to gently spread the toffee over the pretzels.
Bake the pretzels for about 8-10 minutes until golden.
Let the pretzels cool completely before breaking into clusters.
If desired, melt chocolate chips and drizzle over cooled pretzels.