Into a heated, large pan, add the oil or Frylight and add the lamb, and fry for approx 8-10 mins, until browned, stirring occasionally to break any lumps
Remove the meat, drain off any fat, and set aside. Spray the pan with the other squirt of spray, reduce the heat, add the diced onion, carrot, celery, and garlic, and cook over a medium heat for 8 mins, until the onion is softened
Add the herbs, tomato puree & Worcestershire sauce, and fry for a minute or so, before adding the lamb back in
Pour over the stock, bring to a simmer, cover, and cook for 30 mins. After 15 mins, remove the lid, and add the drained lentils
Heat the oven to 180c/ 160 fan, gas 4.
Meanwhile, in a pan of boiling water, boil the potatoes, until cooked, approx 15 mins
Once cooked, drain, add the skimmed milk, season with a pinch of salt and pepper, mash well
Spoon the mince into an oven proof baking dish, remove the bay leaf, and rosemary, (if left whole).
Spread the mash over the top, fluffing with a fork if desired. Bake for 20-25 mins, until golden brown and bubbling
Allow to stand for 5 mins before serving. Garnish with parsley immediately before serving