Place the mince in a non-stick frying pan and cook over a medium heat, stirring until beginning to brown.
Meanwhile, peel and finely chop the onion and carrot. Add to the mince and cook for 2 mins.
Make up the stock cube with 250ml of boiling water from the kettle. Add the flour to the mince, stir well for one minute. Add the stock and bring to the boil, stirring. Cover and cook for 15 minutes or until the mince and vegetables are tender.
Meanwhile, peel the potato and cut into large chunks. Cook in boiling water for 10 minutes or until tender. Drain then mash with the milk.
Divide the mince over the base of four small or one medium ovenproof dish, then top with the potato. If eating straight away, pop the pie under the grill until the top is brown if liked. If serving later, cool, then chill. Bake at 180C/350F/Gas mark 4, for 20-25minutes or until piping hot.