Place the potatoes in a pan of salted, cold water and bring to the boil. Reduce the heat to a simmer and cook the potatoes until tender.
Peel and finely dice the shallots and garlic cloves. Pick the leaves from the parsley and mint and carefully chop. Snip the chives.
Drain the potatoes and then crush with lightly with a fork. Stir in the butter and chopped chives and parsley. Check the seasoning and adjust if necessary.
Preheat the oven to 180'C.
Season the lamb fillets with salt and pepper. Heat a frying pan until hot and add a drizzle of oil. Cook the lamb for around 3 minutes and until browned on all sides. Transfer to the oven and cook for another 5 minutes. Remove from the pan and allow to rest. Reserve the pan and any juices from the lamb for later.
Heat a saucepan over a medium heat and add the butter. Sweat the shallots until soft and then add the garlic. Cook for a minute and then add the peas. Season with salt and pepper and stir in the creme fraiche. Bring to the boil and then finish the sauce with the chopped fresh mint. Add any resting juices from the lamb to this sauce.
Place the potatoes into the middle of a plate, slice the lamb on an angle and place on top, then spoon the peas around the plate.
«Lamb neck fillets are most commonly used in slow cooked dishes. When roasting like this make sure you allow the meat to rest before slicing to ensure that it is tender.»