Cut the clementines into thin slices in cross-section and discard the ends.
Put the granulated sugar and 500ml (17fl oz) cold water into a large pan and heat gently, stirring until dissolved. Bring to a boil and bubble for 5 minutes.
Add the fruit slices and simmer for 2 hours, stirring occasionally, until the peel is translucent and tender.
Preheat the oven to its lowest setting (gas ¼, 110°C, fan 90°C). Drain the slices then, using a fork, transfer to two baking trays lined with nonstick baking paper and bake the citrus slices for 2 hours.
Put the caster sugar in a bowl. Dip each slice into it and place on a wire rack to dry for 1 hour. If not needed immediately, store in an airtight container.
Shortly before giving, melt the chocolate in a heatproof bowl set over a pan of simmering water. Dip the slices into the chocolate to cover half. Place on a tray lined with nonstick baking paper, leave to set at room temperature, then gift wrap.
Store for up to 4 weeks in an airtight container.
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