Place the potatoes in a pan and cover with cold water. Bring to the boil and simmer for 15 minutes.
While the potatoes are cooking, preheat the oven to 200C/400F (fan). Heat the oil in a large frying pan.
Add the onions, celery, and carrot and cook on medium heat for five minutes until they start to soften.
Add the minced lamb and cook until browned – breaking up any pieces as you go.
Add in half the salt and pepper, the Worcestershire sauce, and stock. Simmer for 5 minutes.
By this time, the potatoes should be cooked. Drain the potatoes and mash using a potato ricer.
Add the cream, butter and remaining salt and pepper and mix together.
Mix the cornflour with four tbsp of cold water and stir into the simmering lamb mixture to thicken the sauce (you may need to add a little more if you like it thicker).
Turn off the heat and use a slotted spoon to scoop out the lamb mixture and place it into a 13”x 10.6” (33cmx27cm) baking dish. This should leave most of the gravy behind in the pan.
Top the lamb with the mash potatoes, and flatten out with a spoon.
Rough up the top of the mash with a fork (so you get nice crispy bits).
Place in the oven for 20 minutes until the mashed potato is golden brown.
Heat up the gravy, then serve the shepherd’s pie with the gravy and some green veg.
