Preheat and line pan: Preheat the oven to 250°F and line a large rimmed baking sheet with parchment paper so the caramel doesn't stick.

Combine the dry mix: In a very large bowl, combine the pretzel twists, cereal squares, and mixed nuts, tossing so they're evenly distributed.

Melt the butter: In a medium saucepan over medium heat, melt the unsalted butter completely, swirling the pan occasionally.

Cook the caramel: Stir in the brown sugar, corn syrup, and salt, then bring the mixture to a boil and let it bubble for 2 to 3 minutes until it thickens slightly and smells toasted.

Add vanilla: Remove the saucepan from the heat and stir in the vanilla extract, which will foam up briefly as it combines.

Coat the dry mix: Pour the hot caramel over the pretzel mixture and toss with a large spoon until every piece looks glossy and coated.

Spread on the pan: Spread the coated mix in an even layer across the prepared baking sheet, breaking up any large clumps.

Bake and stir: Bake for 45 minutes total, stirring every 15 minutes, until the mix turns deep golden brown and smells like toffee.

Cool slightly: Remove the pan from the oven and let the mix cool for about 10 minutes, just until it's warm instead of hot.

Melt the white chocolate: Melt the white chocolate chips in 20-second bursts in the microwave, stirring between each, until smooth.

Drizzle and top: Drizzle the melted white chocolate over the warm mix, then scatter the candy-coated chocolate pieces evenly across the top.

Set and break apart: Let the mix sit at room temperature for 20 minutes until the chocolate hardens, then break it into clusters by hand before serving.