In a large bowl combine the Cheerios, Chex, Pretzels and m&m’s. Mix them up a bit, making sure that everything is evenly distributed.
Meanwhile, over a double boiler, melt the white chocolate according to the directions on the package.
Once the chocolate has melted and is a smooth consistency, drizzle the chocolate over the cereal mix and combine with a wooden spoon or hands. Make sure all the cereal is covered in chocolate. If you need to melt the extra white chocolate to cover all the mix then go right on ahead!
Once the entire batch has been combined, lay it out to dry on a large sheet of parchment or wax paper. Let dry for 1 hour so the chocolate is cooled and hard. Break it up into medium pieces and store in an airtight container in the fridge or freezer.