For the oat cereal: Line 2 rimmed baking sheets with parchment paper.
Place the cereal in a large bowl. Pour about half of the tempered chocolate over the cereal and, using a rubber spatula, toss the cereal around to coat evenly. The chocolate will begin to set. When the first coating has set, pour in the remaining chocolate and again toss to coat evenly.
Working quickly while the chocolate is still pliable, scoop up small mounds of the cereal and place them on the prepared baking sheets. Set aside for about 30 minutes (or place the baking sheets in the refrigerator for no more than 10 minutes to speed the setting).
Layer the cereal clusters, separated by sheets of waxed paper, in an airtight container and store at room temperature for up to 2 weeks.
For the corn flake cereal: Crunch up the cereal by hand, so as to break them up, but not pulverize them into crumbs. Add the crumbled cereal to the bowl of chocolate and toss to coat evenly.
Drop the cereal by rounded spoonfuls onto a parchment lined baking sheet. Place the sheet into the refrigerator to help the cornflake clusters set.
Package as you wish!
Cook's Note: Tempering, which requires more patience and care than skill, can be done in a variety of ways, but the end result must always be the same: a smooth, pure chocolate that will retain its satiny texture and shiny color once it has set. It can be done 3 different ways. 1) the demanding traditional, time-consuming (and messy) French way, called tabliering whereby two-thirds of the full amount of melted chocolate is poured out onto a cool surface and worked with a spatula until it reaches 81 degrees F and then worked back into the remaining melted chocolate until the whole mass is of a uniform temperature; 2) simply by working with the chocolate over a hot water bath; 3) in a microwave oven. Since the chocolate must reach and maintain an exact temperature in each case, you need a perfectly calibrated thermometer. I rely on a digital laser thermometer, which is a good investment if you want to make tempering an easy job.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.