Heat the orange juice in a medium-size pan until nearly boiling. Cover the gelatine with cold water and leave for 5 mins until spongy and softened. Squeeze out any excess water. Take the pan off the heat and stir in the gelatine until dissolved. Let the mixture cool a little, then divide between 10 serving dishes. Place in the fridge for at least 5 hrs, or preferably overnight.
Cover a baking sheet with some baking parchment. Melt the chocolate either in the microwave (1-2 mins should do it) or in a bowl set over a small pan of boiling water. Pour the melted chocolate into a small freezer bag. Make a piping bag by snipping off a tiny piece of one corner. Now pipe out 10 spider-web shapes onto the baking parchment: pipe a circle with a smaller circle inside, then pipe lines coming out from the centre like the spokes of a wheel. Place the chocolate spider webs in the fridge to harden. Just before serving, carefully peel away each spider web from the parchment and place on top of a jelly.