Peel and chop the potatoes, then boil them in salted water until tender. Drain the potatoes and mash them with butter, milk, salt, and pepper until smooth and creamy.

While the potatoes are cooking, brown the beef mince in a large ovenproof pan or casserole dish. Drain any excess fat, then add the chopped onion and diced carrots, cooking until softened.

Stir in the beef stock, bring to a simmer, and cook for 5-7 minutes until slightly thickened. Spread the mashed potato topping evenly over the beef filling, then bake in a preheated oven at 190°C (375°F) for 20-25 minutes, or until the topping is golden brown and the filling is bubbling.