Place a silpat mat or parchment paper on a baking sheet. If using parchment paper lightly spray it with cooking spray. Spray a spatula with cooking spray and set aside.

Place the sugar and water in a heavy bottomed saucepan and stir to combine. Place pan over medium-high heat and stir just until the sugar is dissolved. Once the sugar comes to a boil do not stir the mixture. If it is cooking unevenly gently swirl the pan. Cook until the mixture turns a medium amber color. Remove the pan from the heat and stir in the rice cereal until it is coated with the sugar mixture. Turn the mixture out onto the prepared pan and spread it as thin as possible using the greased spatula.

Let the caramelized rice cereal cool. Break it into pieces and place it in a large zip-top bag. Using a rolling pin, crush the pieces until they are the size of one or two pieces of rice.

Place a piece of parchment paper on a baking sheet. Temper or melt the chocolate. (The easiest way to melt chocolate is in a microwave on 50% power. Stir every 30 seconds to prevent the chocolate from burning.) Spread the chocolate on the parchment paper into a layer approximately ¼ inch thick. Sprinkle the chocolate with the caramelized cereal. Press down lightly on the cereal to insure that it sticks to the chocolate. Place in the refrigerator for a few minutes until the chocolate sets.

Break into pieces and store in an airtight container. If using tempered chocolate store the chocolate at room temperature. If not, store the bark in the refrigerator.