1 (17.5 ounce) package crispy corn cereal squares (such as Corn Chex®)
1 (16 ounce) jar salted dry-roasted peanuts
1 (14 ounce) package candy-coated milk chocolate pieces (such as M&M's®)
24 ounces white chocolate, chopped
Cover a large area of counter space with waxed paper and tape it down. Mix pretzels, corn cereal squares, peanuts, and candy-coated milk chocolate pieces together in a large bowl. Melt white chocolate in the top of a double boiler over simmering water, stirring frequently and scraping down the sides with a rubber spatula to avoid scorching. Pour melted white chocolate over pretzel mixture; stir to evenly coat. Quickly transfer mixture to the prepared waxed paper and spread in a thin layer; cool completely. Break into pieces and store in an airtight container.