Warm your cream up in a saucepan on a medium heat. Do not allow it to boil. Add the butter. Remove your mixture from the heat and break your chocolate into the mixture. Using a whisk gently stir so the chocolate melts.
If your mixture splits a little add a splash of cold tap water. Add a whole orange worth of zest to your chocolate mixture and ginger.
Whisk quite firmly so all the mixture combines. Add a pinch of salt and give it one further whisk.
Pour your mixture into a bowl and place in the fridge for 2 hours – stirring every 15 minutes or so. After 45 minutes, mixture will thicken quickly, so stir every 3 to 5 minutes until thick enough to scoop, 10 to 20 minutes more. Using two spoons or a small ice-cream scoop, form into 1-inch balls; transfer to a parchment-lined baking sheet.
Grate your other orange’s zest into the cocoa powder and mix with a spoon.
Using a small spoon get some truffle mixture and using your hands mould into balls, then dip into the orange cocoa powder making sure it’s all covered.
Pop them into small truffle cases and then back into the fridge to keep them solid.