Line a large sheet pan with parchment paper and set aside.
In a very large bowl, combine the Corn Chex, mini pretzel twists, Rice Chex, Honey Nut Cheerios, and 1 cup Valentine’s M&M’s. Stir to combine.
In a medium microwave-safe bowl, combine 3 cups white chocolate chips and the vegetable oil. Microwave for 30 seconds, stir for 15 seconds, and microwave another 15 seconds. Stir until melted and smooth. If needed, return to the microwave for a bit longer. (Bursts of 15 seconds stirring for 10 seconds in between each burst). Pour the melted and smooth white chocolate over the snack mix.
Working quickly, gently stir until all ingredients are coated in white chocolate, then quickly transfer to the prepared sheet pan and spread into an even layer. Immediately add the remaining Valentine’s M&M’s on top and optional sprinkles. Optional step: Melt the last 1/4 cup white chocolate chips in the microwave and transfer them to a small plastic bag. Cut the tip off the bag and pipe stripes across the white chocolate snack mix.
Allow white chocolate to firm up and harden at room temperature or place in the fridge until firm, about 10–20 minutes. Break into pieces and serve.
Video
Notes
Storage: Store in an airtight container at room temperature. Or freeze in a sealed container or bag for longer shelf life.