Add the ground meat and continue to cook over low heat until meat is brown. Add vegetables, water, salt, pepper and chilli powder if used and cook until done and fairly dry. Add chopped fresh herbs just before turning off the heat.
Peel and mash boiled potatoes with milk, salt, grated cheese and half the butter.
Spread the cooked meat evenly in a baking dish. Top with mashed potatoes, spreading evenly to cover filling completely.
Make swirl patterns on surface of potatoes with a fork and dot with the remaining butter.
Bake for about 30 minutes until the potato topping is golden and filling is hot.