Preheat the oven to 180oC / 160oC Fan / 350oF / Gas mark 4
Place the chopped potatoes in a saucepan of salted cold water. Bring to the boil, reduce the heat and simmer for 15 - 20 minutes or until they are cooked through and soft when pierced with a knife. Drain well and set aside for later.
Meanwhile, spray the bottom of a large saucepan with Frylight/ Pam (10 - 15 pumps). Place over a medium heat and add the chopped onion, carrots, celery and garlic. Saute for about 8 - 10 minutes, until the onions are translucent and the carrots have softened. Add the red wine vinegar to de-glaze the pan (see notes in post).
Add the mince beef / ground beef and cook for 5 - 6 minutes until it has browned.
Add the tomato puree, Worcestershire sauce, tin of tomatoes, beef stock and bay leaves and stir to combine. Bring to the boil, then reduce the heat and leave to simmer for 15 - 20 minutes, stirring occasionally.
Mash the potatoes with the half fat butter and the milk. Season with salt and pepper.
Once cooked, spoon the mince beef / ground beef mixture into a casserole dish (approx 8 inch square). Dot spoonfuls of the mashed potato on top of the beef mixture and use a fork to spread it evenly over the top.
Bake for 30 - 35 minutes or until the potato have turned golden brown.
Serve on its own or with garden peas or sweetcorn if you prefer.