Prep your workspace: Line a large baking sheet with parchment or wax paper. This is where the chow will set after mixing.
Combine the dry mix: In a large bowl, add cereal squares, pretzels, and peanuts. Toss gently to distribute evenly.
Add the soft mix-ins: Stir in mini marshmallows and half of the chocolate candies.
Save the rest for topping so they stay colorful and intact.
Melt the white chocolate: Place the chopped white chocolate and oil (if using) in a microwave-safe bowl. Microwave in 20–30 second bursts, stirring after each, until smooth. Alternatively, melt in a heatproof bowl over a pot of gently simmering water, stirring constantly.
Coat the mixture: Pour the melted white chocolate over the cereal mixture.
Use a spatula to fold gently until everything is evenly coated. Work quickly so the chocolate doesn’t set before it spreads.
Spread and top: Transfer the mixture to the lined baking sheet and spread into an even layer. Sprinkle the remaining chocolate candies and the holiday sprinkles over the top.
Add a light pinch of flaky sea salt if you like that sweet-salty pop.
Let it set: Allow the mixture to sit at room temperature until firm, about 20–30 minutes. For faster setting, refrigerate for 10–15 minutes.
Break into pieces: Once firm, break into chunks. Aim for a mix of larger clusters and bite-sized pieces.
Serve or store: Enjoy right away or transfer to airtight containers for later.