4 leaves platinum grade gelatine or 9 leaves regular gelatin, soaked in water for 10 minutes.
Heat the lactose free double cream in a small pan until it comes to the boil.
Remove from the heat, then stir in the cocoa and stir continuously until the cocoa has completely melted.
Grate the zest of four oranges and add it to the chocolate cream.
Squeeze the juice from two oranges and add eight tablespoons of the juice to the chocolate mixture with the sugar. Set aside all the remaining oranges.
When the gelatin has softened, remove it from the water, shake off any excess water and place the gelatine into the hot chocolate mixture - stir until dissolved.
Strain the mixture through a sieve and then divide equally between serving glasses or dishes.
Place in the fridge and allow the panna cotta to set overnight or for at least six hours.
Meanwhile, prepare the orange segments. Using a serrated knife, cut off all the peel and white pith from the remaining oranges (including the one that you have zested), working over a bowl to catch the juices.
Cut between the orange membranes to remove the segments. Place the orange segments into the juice and chill in the fridge with the panna cottas.