1Heat a drizzle of oil in a large non-stick pan. Add the leek and cabbage and fry on a medium heat for 5 minutes, stirring regularly until soft.
2Remove the leek and cabbage from the pan and set aside.
3Place the potatoes in cold, salted water. Bring to the boil and simmer until soft enough to mash.
4In the meantime, add another drizzle of oil to the pan you fried the leek and cabbage in. Add the onion and carrot, fry on a medium heat for 5 minutes.
5Add the beef mince and fry on a medium for 5 minutes until browned. Drain any excess oil.
6Stir in the flour, ketchup and garlic until the flour has disappeared. Fry for a minute or two until sizzling.
7Slowly add the stock a little at a time, bringing it to the boil each time before adding more. When all the stock is used up, stir in the worcestershire sauce and frozen peas. Season with salt and pepper. Bring it back to the boil before simmering for 15 minutes until you have a thick sauce.
8Heat the oven to 200C Fan.
9When the potatoes are cooked, drain them and mash them with a fork, followed by a potato masher.
10Stir in the butter and cream and season with salt and pepper. Add the cabbage and leek to the mash and stir until combined.
11Tip the mashed potato into a baking dish. Smooth until even. Pour the beef mince over the top and even it out.
12Cover it in grated cheese and bake in the oven for 25 minutes until the cheese is melted and golden brown.