Mix everything from the Day 1 list of ingredients together in a large mixing bowl. Cover with cling film and leave to marinate overnight.
Add the rest of the ingredients from Day 2 and stir together really well.
Butter a pudding basin, and slice the extra clementine, tucking the slices into the bottom of the basin.
Fill the pudding basin with the pudding mixture then prepare the basin for the steam.
Take a piece of greaseproof paper and lie a piece of foil on top, make a fold in the centre of both pieces which allows for more room for the steam to rise. Place these over the top of the pudding basin, with the foil on top, securing with string around the pudding. Trim off any excess paper and foil, you don't want them to hanging too low as otherwise they will soak up the water during the steam.
Place a wire rack (or a folded up tea towel) into a large lidded pot, deep enough to cover the pudding. Then place the pudding on top of the rack.
Fill the pot up with boiling water until halfway up the pudding. The water should not touch the greaseproof paper or foil otherwise they will soak it up and the pudding will go soggy. Place the lid on the pot and turn the heat on so the water is kept at a simmer.
Steam for four hours, checking the water level occasionally and topping up if necessary.
Remove the pudding from its pot then leave to cool. Once cool re-wrap the pudding in fresh greaseproof paper and foil and store in a cool dark place until Christmas Day.
On Christmas Day the puddings will need a final steam before serving so repeat steps 6 and 7. However your pudding will only need two hours this time.
Turn your pudding out onto a plate and serve with the Cointreau sauce.