Pre-heat oven to 180deg C (fan)/gas 3.

Heat a frying pan and fry off the lamb mince until browned.

Drain most of the fat, leaving about 1 tbsp, and caramelise the mince on each side 2-3 times.

Remove mince to a casserole dish.

Fry the diced lamb kidneys quickly in the hot pan and add to the mince in the casserole dish.

Add the chopped onion and sliced carrots to the pan and fry until golden and softened, about 10 minutes.

Drain off the remaining fat from the onions and carrots.

Add the plain flour to the vegetables and cook for about a minute.

Add the Worcestershire sauce and lamb stock (in two parts), stirring well to thicken into a gravy.

Add the gravy mixture to the mince and kidneys in the casserole dish and mix.

Arrange the thinly sliced potatoes over the top of the mixture.

Brush the potatoes with melted butter or olive oil and season with salt and pepper.

Cover the casserole dish and place in the oven for about 1 hour and a half.

Remove from the oven and spoon off any liquid fat that has risen to the surface.

Increase the oven temperature to 220 deg C.

Return the casserole dish to the oven, uncovered, to brown the potatoes, or use the grill.