Put the ice in a large bowl and set aside.

Reserve a handful of the chopped chocolate, and melt the rest gently in a stainless-steel bowl set over simmering water until it reaches 115°F/45°C on a candy thermometer. Remove the bowl from the heat. Wipe the bottom of the bowl with a dry cloth to prevent water from splashing onto the work surface.

Sprinkle the reserved chocolate into the melted chocolate and stir. Cool the chocolate by placing over the bowl of ice for a few seconds at a time, removing it, stirring until smooth, and repeating until the temperature drops to 82°F/31°C.

Heat the chocolate again by placing the chocolate bowl back over the simmering water for 30 seconds to 1 minute at a time. Once its temperature rises to 89°F/34°C, the chocolate is ready to use in candy bar production.