Combine the puffed rice cereal with the simple syrup in a bowl. Toss to coat the puffed rice.
Place the syrup-coated rice on a parchment paper–lined sheet pan in a single layer and bake until the moisture evaporates. The intention is to cover the puffed rice with a coat of sugar that will protect it from moisture.
Once the puffed rice has cooled, place it in a bowl and combine with the tempered chocolate. Adjust the amount if necessary, using only enough to coat the puffed rice, not to make clusters of it.
Using a demitasse spoon, scoop 5g / .03oz amounts of the chocolate-covered puffed rice onto a sheet pan lined with a nonstick rubber mat. Let the chocolate set at room temperature.
Reserve in an airtight container at room temperature. This can have a long shelf life if it never comes into contact with any kind of moisture. Taste daily to ensure freshness.