Heat olive oil in a large deep pan or casserole dish, add chicken, season with salt and pepper and cook for 5 mins. Add leek, carrot, celery and onion and continue to cook for 5 mins, until veg has softened. Add garlic and rosemary and cook for 2-3 mins before adding chicken stock, milk, oregano, smoked paprika, cloves, bay leaves, Worcestershire sauce and ham, bring the pan to a low simmer and leave to cook for 30 mins.

Meanwhile, bring a lightly salted saucepan of water to boil and and cook potatoes until soft, approx 15 mins. Once cooked, drain and add potatoes back to saucepan. Then, add butter, salt and pepper to taste and mash together until smooth with no lumps. Add milk and chives, then using a spoon whip mash together until creamy and smooth.

Back to the pie filling - add butter, white wine vinegar and cornflour mixed with water. Stir well and continue to cook on a low simmer for 10-15 mins, until sauce thickens. Stir in frozen peas and then remove from heat.

Transfer pie filling to baking dish, then top with creamy mash. Spread and flatten mash, then top with grated cheddar, add some black pepper then bake pie for 20 mins, until cheese is bubbling.