Line a baking sheet with parchment paper. Spread the crushed pretzels evenly over the prepared baking sheet.
In a medium saucepan, combine butter, 1 cup granulated sugar, corn syrup, and salt. Cook over medium heat, stirring constantly, until the butter is melted and the sugar is dissolved.
Bring the mixture to a boil and continue to cook, stirring occasionally, for about 10-15 minutes, or until it reaches the hard-ball stage (250-265°F or 121-129°C) on a candy thermometer. Be careful not to scorch the mixture.
Remove the saucepan from the heat and stir in the vanilla extract.
Carefully pour the hot toffee mixture evenly over the crushed pretzels on the baking sheet. Spread it quickly with a heat-resistant spatula if needed.
While the toffee is still warm and slightly soft, sprinkle the cinnamon sugar mixture evenly over the top. Gently press it down with the spatula.
Let the churro toffee cool completely at room temperature, about 30 minutes to 1 hour, until hardened.
Once cooled and hardened, break the churro toffee into pieces. Store in an airtight container at room temperature.
Notes
For a richer flavor, you can add a pinch of cinnamon to the toffee mixture itself before pouring. Enjoy!