Heat the oil in a shallow flameproof casserole or a saucepan over a medium heat. Add the onion, carrots and garlic and fry for about 5–6 minutes until softened.
Add the red wine and tomato purée and bring to the boil. Turn the heat down to a simmer and add the stock or gravy, Worcestershire sauce, redcurrant jelly and rosemary. Add the lamb, peas and parsley and season with salt and pepper. Simmer gently on a low heat while you prepare the potatoes.
Preheat the oven to 200C/180C Fan/Gas 6.
Boil the potatoes in a pan of salted water for 10–12 minutes until tender, then drain. Heat the butter and cream in the pan, pass the potatoes through a ricer into the pan of butter and cream (or mash well). Mix well to form a creamy mash without any lumps. Season with salt and pepper.
If not using a casserole, transfer the lamb mixture into an ovenproof pie dish. Top the lamb with the mashed potato.
Bake for 25 minutes or until golden-brown and bubbling.
