Dice the lamb, season with salt, season with pepper. Heat oil in a frying pan, brown meat in portions.
Add cinnamon, garlic, ginger, cumin, curry, turmeric and mace and fry briefly.
Transfer everything to a suitable saucepan. Add the lamb stock and cook for fifty minutes at low temperature with the lid closed.
Add the whipped cream and cook for another thirty minutes without the lid, boiling the sauce a little.
Melt the cornstarch in the water, fold in and cook for two minutes, season with salt and freshly ground pepper to taste.
Remove the skin from the apple, cut into quarters, remove the core, cut the apple into fine slices and add to the curry.
Pluck coriander greens from the stems, chop coarsely, and mix into the curry shortly before serving.
Serve with long-grain rice.