Score the fat side of the lamb with a knife, season with salt and pepper, rub all over with the mint, place in a bowl with the mint and pour over the oil, cover and leave over night to marinade
Tip the red cabbage into a large pan with the red onion, brown sugar, cider vinegar, red wine, butter and cinnamon stick and season well. Bring to a simmer, then cover with a lid, lower the heat and cook for 1 1/ 2 hrs. stirring every so often. Remove the lid and continue cooking for 30 mins until tender. Can be made in advance and reheated as it will keep for two days, or can be frozen for one month
Peel and cube potatoes and add to pot with enough water to cover plus an inch. Bring to a boil, lower to a simmer, and cook for about 20 minutes. Potatoes are done when a fork or knife inserts and removes easily.
In a saucepan, heat cream, butter and the 5 sprigs of mint over low heat and bring to a simmer.
Strain mint from cream and add to potatoes. Then add cream and heat through.
Add butter, and chopped mint.
Mash and season to taste.
Heat a Pan to medium heat, add the lamb season with salt and pepper and seal on all sides, when sealed transfer to pre – heated oven 180c/356f/gas mark 4 and cook for 15 mins approx. to give you a slightly pink finish, cook longer of you want it better done.
Remove from the oven, let it rest for 2 minutes, remove and discard the skin layer, and carve the meat.
For the sauce add all ingredients into a pot and boil down to a nice consistency, ten strain
Place a nice spoon of cabbage on plate, with a nice shaped spoon of mash, place lamb decoratively on plate and finish with sauce